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Question: Downshifting gears in a Shifter Kart (TM K9)


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#1 Kart15

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Posted 17 October 2013 - 22:20

Hello

 

Im about to buy a Shifter Kart (TM K9), but I never raced karts with gears before. I have experience in Formula Vee and touring cars, both with the normal H-pattern and normal clutch. So I want to know if in shifter karts I have to do the famous "heel toe" technique, touching a little bit the throttle pedal while I downshift the gears down or this is unecessary and I have only to brake and downshift the gears down without touch the throttle pedal.

 

Thanks!  :yawnface:


Edited by Kart15, 17 October 2013 - 22:20.


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#2 bigleagueslider

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Posted 18 October 2013 - 05:29

Shifter karts only have two pedals, brake and throttle.  The clutch is hand operated, and is only used for starts.  The brake and throttle pedals are located on opposite sides of the steering column, left foot for braking and right foot for throttle.  Since there is no clutch pedal, there would seem to be no reason for using the "famous heel toe technique".  In fact, shifter karts are a great way for single seat race drivers to learn left-foot braking techniques.



#3 Kart15

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Posted 18 October 2013 - 15:13

Yes, but what´s about the techinique to avoid the rear wheels locking in the braking? This video of an USF2000 car for example, he also has only the throttle and brake pedal, driving with the left-foot braking technique, like in a shifter kart, but he touch a little bit the throttle while he downshifts, even with a non clutched car:

http://www.youtube.c...h?v=aN7Xz4erapw

 

Why you don´t need to tho this in a shifter kart and need to do this in a formula car with only two pedals like the shifter kart?



#4 Ross Stonefeld

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Posted 18 October 2013 - 17:34

I think an F2000 is an H-pattern, so really does need a blip.

 

Plus maybe it needs it because it's a slightly different engine than a shifter kart?

 

Though I knew guys who raced British Formula Ford back when it was an elite series, and they looked at me like I was speaking Latin when I talked about clutches. 



#5 Kart15

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Posted 18 October 2013 - 19:05

Yes, you´re right, I saw now, F2000 is H-pattern. So the final veredict is that you don´t need a blip in the throttle when downshifting in a shifter kart or in a sequencial gearbox formula, because you can downshift so fast that a blip is not necessary? Sure if you not gonna break the gearbox downshifting without a blip in the throttle?



#6 Nathan Thompson

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Posted 18 October 2013 - 22:33

In a sequential or H pattern box, if there is no provision for the automatic matching of layshaft speed and mainshaft speed, then a blip is required for a smooth and mechanically sympathetic down change. Your kart will most likely not have such a provision, so you will need to blip your downshifts. You can downshift without blipping, but it probably will upset the kart and put undue strain on the dog rings, shift forks, and drum, and will also stress the chain. Racing sequential and H pattern boxes only differ in how the gears are selected, the gears are engaged by dogs in both types. Even F1 cars blip on down changes, but the ECU and hydraulic system operating the throttle and gearbox do this instead of the driver.



#7 Kart15

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Posted 19 October 2013 - 01:32

Now I´m confused, you told me that if I downshift whitout blipping I will stress the chain, but some people are telling me that if I brake and blip the throttle at the same time, I will break the chain.. In normal karts with engines like Parrilla, PCR etc, if you brake and accelerate at the same time you will break your chain.. I watched some shifter kart onboard videos and I didn´t see nobody blipping..

 

Look, my impression is that the downshifting is so fast that you don´t have time to blip

 

http://www.youtube.c...h?v=MdVfBcWAzeo


Edited by Kart15, 19 October 2013 - 01:38.


#8 Kart15

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Posted 19 October 2013 - 01:50

One more video, racing a Shifter in Daytona and he doesn´t seem to blip the throttle in the downshifting

 

http://www.youtube.c...h?v=au9NIx9-xjQ



#9 Nathan Thompson

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Posted 19 October 2013 - 04:57

Like I said, it is possible to downshift your kart without blipping and if you keep within your motor builders suggested maintenance schedule you'll probably be fine. Probably. But, it is without a doubt harsher on the internals of the gearbox to do it without blipping. It all happens no quicker than with an h pattern, a skilled driver can go from top to first in an h pattern without skipping gears and with blipping, just as fast as he can with a sequential.

And yes, blipping may stress the chain a bit, but so does bump starting the kart, standing starts, and locking up the brakes.

I feel I've correctly answered your question from a technical standpoint. However, the most important thing is to do what is most comfortable for yourself as the driver.



#10 BS1

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Posted 19 October 2013 - 18:57

Some blip, but it is not necessary. I wouldn't worry about it that much as it will work itself out when you get into the kart.



#11 Kelpiecross

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Posted 21 October 2013 - 13:09

As I understand it - with a sequential motorcycle-type gearbox there is no reliable way of finding a "neutral" between gears - that is - there must be a point where no gears are engaged during a change up or down but you can't really find it. To blip the engine surely you would need a point where the engine is not connected to the wheels - either by finding a "neutral" or by using the clutch.
Somebody wrote that the SuperKart clutch is used only for starting from rest - therefore essentially you can't "blip" the throttle during down changes anyhow which is probably why the kart in the Daytona video doesn't do it.

Remember that the basic idea of "blipping" on down changes comes from the era when cars had no synchromesh or synchro only on some gears - especially as the non-synchro gears were almost always sliding-mesh rather than constant-mesh. I think I am correct in saying that most cars from England and the USA up to the mid-sixties had a sliding-mesh first gear. Being a competent driving meant being able to pick up first gear when on the move - hopefully with little or no crunching - otherwise the car had to be stationary to engage first gear. Also typically early Minis and Jags seemed to quickly wear out the synchros on all their gears so you had to "double-declutch" anyhow - even on upchanges if the synchro was really lacking. Oddly enough if you made some attempt to "double-declutch" a Mini etc. gearbox from new the synchro never seemed to wear out.

I am pretty sure that most of the oldtimers (and maybe not so oldtimer) on this forum would be familiar with all of the above. I drove a '71 Landcruiser in the early '70's and it was three-speeds and no synchro on first - and you really did need to able to pick up first on the move in rough country.

#12 bigleagueslider

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Posted 22 October 2013 - 06:06

Shifter karts use a hand operated clutch.  Also, most shifter karts use 2-stroke engines which are quite sensitive to rpms.  You must also consider that a shifter cart is not much heavier than a motorcycle, and the shifter karts mostly use motorcycle engines and gearboxes.  Since the rear wheels on a shifter kart are far smaller in diameter than a motorcycle they naturally spin at much higher rpms, and thus the forces transmitted thru the chain final drive are also lower.



#13 Fat Boy

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Posted 22 October 2013 - 16:49

You only use the clutch of a race kart for the launch. It's not made or even advantageous for general use.

 

For upshifts, you just lift enough to release the pressure on the gears (between the dog-rings / gear dogs). The actual time that you need to lift for shifting is literally as fast as you can move your foot. If you were able to do it with electronics, the total shift cut time would be less than 1/20th of a second.

 

For downshifts, you do not need to blip. Having said that, I always did when I raced them. It was kind of a 'method' thing. If I were given the chance to race/drive anything else, I wanted that  muscle memory built into my head. You just do the  same thing on the downshift that you do on the upshift (only backwards). The blip only needs to be about 25-50% throttle and for a fraction of a second. Again, you're just trying to reduce the pressure of the driveline holding the dog ring and dog together.

 

The fastest guys driving shifter karts that I know (national champion level) never blipped on downshifts. They made their downshifts very fast and very late. The 'shock' to the driveline is very small because of next to no rotational inertia of a kart engine and the fact that they would make the downshifts so late. What they did/do on a racetrack is a completely different animal than what I did.


Edited by Fat Boy, 22 October 2013 - 16:50.


#14 Kelpiecross

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Posted 23 October 2013 - 03:24

You only use the clutch of a race kart for the launch. It's not made or even advantageous for general use.
 
For upshifts, you just lift enough to release the pressure on the gears (between the dog-rings / gear dogs). The actual time that you need to lift for shifting is literally as fast as you can move your foot. If you were able to do it with electronics, the total shift cut time would be less than 1/20th of a second.
 
For downshifts, you do not need to blip. Having said that, I always did when I raced them. It was kind of a 'method' thing. If I were given the chance to race/drive anything else, I wanted that  muscle memory built into my head. You just do the  same thing on the downshift that you do on the upshift (only backwards). The blip only needs to be about 25-50% throttle and for a fraction of a second. Again, you're just trying to reduce the pressure of the driveline holding the dog ring and dog together.
 
The fastest guys driving shifter karts that I know (national champion level) never blipped on downshifts. They made their downshifts very fast and very late. The 'shock' to the driveline is very small because of next to no rotational inertia of a kart engine and the fact that they would make the downshifts so late. What they did/do on a racetrack is a completely different animal than what I did.


But just how did you briefly disconnect the engine from the wheels to allow the "blip" - clutch or some other method?

I know what you mean by "method" and "memory" - I literally don't like to even think about left foot braking, or driving on the "wrong" side of the road (that is; the right hand side) or changing gear with my right hand.

#15 Kart15

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Posted 23 October 2013 - 14:55

Very interesting answers, thank you guys, you just helped me to kill this doubt, because when driving Formula Vee and vintage touring cars in my country, I found a very pleasant thing to do the heel toe technique, but these cars are equipped with a H pattern gearbox and you have more "space" between the gears to do the heel toe. Having said that, I found a little nonsense have to blip the throttle in a shifter kart, because in my mind it "cancels" the advantage of a sequencial gearbox..

 

Another doubt: in NASCAR races in road courses, I noticed that drivers who brake with left foot always blip the throttle, while drivers who brake with the right foot always do the normal heel toe technique.. My question is, if you try to drive these cars with left foot breaking, but whitout blipping the throttle in the downshifts, you will not be able to downshift or you will breake the gearbox?

 

Here is a video of Max Papis demonstranting the two techniques:

 

http://www.youtube.c...h?v=-jQC_g_3O1E

 

Is not better to do the normal heel toe technique than have the "advantage" of left foot braking but having to "wait" the time to blip while you find the neutral between the gears?



#16 Ross Stonefeld

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Posted 23 October 2013 - 20:02

You don't drive a Cup car at 10/10ths on a road course(or anywhere really). If you were doing qualifying-style downshifts the gearbox wouldn't last long. Nor would the brakes. So at race pace they have plenty of time to do deliberate downchanges.

 

But you have to blip. Otherwise those things will lock the rear and it's not something you can just flick into a corner and survive.



#17 Fat Boy

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Posted 23 October 2013 - 22:27

But just how did you briefly disconnect the engine from the wheels to allow the "blip" - clutch or some other method?

I know what you mean by "method" and "memory" - I literally don't like to even think about left foot braking, or driving on the "wrong" side of the road (that is; the right hand side) or changing gear with my right hand.

 

I'm going to guess that you need to understand how a racing gearbox (sequential or H-pattern). The people mentioning sychromesh gears are off base. Racing (or kart/motorcycle) gearboxes do not have synchros. So first, investigate the design a bit on your own. Now here's how it works in practice.

 

For a downshift. Put some pressure (a couple pounds) on lever in the downshift direction. The gearbox has some pressure on the dogs-dog ring interface which is holding it in gear. Blip the throttle (say, 25% as fast as your foot can go in-out). As you blip, increase the pressure on the lever. At some point as the engine responds to the blip it will release the pressure on the dog faces and the gearbox will be allowed to shift into the next lower gear. Done properly, it happens *almost* on it's own.

 

It's the reverse on the upshift side. Put pressure on the lever. Lift to reduce the pressure on the gears. Once you lift the gear lever will be allowed to move and you shift the gear. The throttle lift and reapplication should again be as quick as possible.

 

Between every gearset (1>2, 2>3, etc) there is a point where there is no gear engaged. It's a small but completely usable window. The gear selector forks and dog rings travel through these windows between every shift. If a box gets stuck between gears for any reason, it's refered to as 'being in a false neutral'. The only 'real' neutral in a sequential box is either between 1st and second or between first and reverse. This has to do with how the barrel 'star' detents machined and the designers choice.



#18 Kart15

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Posted 24 October 2013 - 01:36

You don't drive a Cup car at 10/10ths on a road course(or anywhere really). If you were doing qualifying-style downshifts the gearbox wouldn't last long. Nor would the brakes. So at race pace they have plenty of time to do deliberate downchanges.

 

But you have to blip. Otherwise those things will lock the rear and it's not something you can just flick into a corner and survive.

 

But are you saying this because all the peculiarities of the Cup cars? Because look the example of this BTCC video, the driver is downshifting without the clutch and without blipping (as I have to do in my shifter kart?) So why in a Cup car you will lock the rear if downshift whitout blipping or heel toe and in this BTCC car not?

http://www.youtube.c...h?v=cOjpHRwgG_k


Edited by Kart15, 24 October 2013 - 01:38.


#19 Kelpiecross

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Posted 24 October 2013 - 03:13

I'm going to guess that you need to understand how a racing gearbox (sequential or H-pattern). The people mentioning sychromesh gears are off base. Racing (or kart/motorcycle) gearboxes do not have synchros. So first, investigate the design a bit on your own. Now here's how it works in practice.
 
For a downshift. Put some pressure (a couple pounds) on lever in the downshift direction. The gearbox has some pressure on the dogs-dog ring interface which is holding it in gear. Blip the throttle (say, 25% as fast as your foot can go in-out). As you blip, increase the pressure on the lever. At some point as the engine responds to the blip it will release the pressure on the dog faces and the gearbox will be allowed to shift into the next lower gear. Done properly, it happens *almost* on it's own.
 
It's the reverse on the upshift side. Put pressure on the lever. Lift to reduce the pressure on the gears. Once you lift the gear lever will be allowed to move and you shift the gear. The throttle lift and reapplication should again be as quick as possible.
 
Between every gearset (1>2, 2>3, etc) there is a point where there is no gear engaged. It's a small but completely usable window. The gear selector forks and dog rings travel through these windows between every shift. If a box gets stuck between gears for any reason, it's refered to as 'being in a false neutral'. The only 'real' neutral in a sequential box is either between 1st and second or between first and reverse. This has to do with how the barrel 'star' detents machined and the designers choice.


So the answer to my question is that you can find a "neutral" between gears in a sequential gearbox.

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#20 Fat Boy

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Posted 24 October 2013 - 03:40

So the answer to my question is that you can find a "neutral" between gears in a sequential gearbox.

Correct.



#21 Fat Boy

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Posted 24 October 2013 - 03:45

But are you saying this because all the peculiarities of the Cup cars? Because look the example of this BTCC video, the driver is downshifting without the clutch and without blipping (as I have to do in my shifter kart?) So why in a Cup car you will lock the rear if downshift whitout blipping or heel toe and in this BTCC car not?

http://www.youtube.c...h?v=cOjpHRwgG_k

 

Cup cars are extremely sensitive to downshifts. For one thing the gearboxes that they use are not the cleanest shifting things. They've gotten much, much better over the years, but you aren't going to mistake it for an Xtrac. Second, the rear suspension of a Cup car is very prone to wheelhop while braking. Once you get the thing hopping around you basically can't turn the steering wheel because the rear end has very little grip. Making very smooth (often clutched) downshifts helps this.

 

I've known guys that if they had a big brake zone that goes from 6th gear to first on a bumpy street course will clutch on the downshifts to avoid wheelhop. That was in a formula car with a sequential box.



#22 Ross Stonefeld

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Posted 24 October 2013 - 11:53

A lot of BTCC cars are front wheel drive too. And the car in that video is a sequential shifter. 



#23 Kart15

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Posted 25 October 2013 - 00:46

Cup cars are extremely sensitive to downshifts. For one thing the gearboxes that they use are not the cleanest shifting things. They've gotten much, much better over the years, but you aren't going to mistake it for an Xtrac. Second, the rear suspension of a Cup car is very prone to wheelhop while braking. Once you get the thing hopping around you basically can't turn the steering wheel because the rear end has very little grip. Making very smooth (often clutched) downshifts helps this.

 

I've known guys that if they had a big brake zone that goes from 6th gear to first on a bumpy street course will clutch on the downshifts to avoid wheelhop. That was in a formula car with a sequential box.

 

So if one day I have the opportunity to drive a NASCAR car, I have the obligation to do the heel toe or blip?



#24 bigleagueslider

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Posted 26 October 2013 - 02:48

Cup cars are extremely sensitive to downshifts. For one thing the gearboxes that they use are not the cleanest shifting things. They've gotten much, much better over the years, but you aren't going to mistake it for an Xtrac. Second, the rear suspension of a Cup car is very prone to wheelhop while braking. Once you get the thing hopping around you basically can't turn the steering wheel because the rear end has very little grip. Making very smooth (often clutched) downshifts helps this.

 

I've known guys that if they had a big brake zone that goes from 6th gear to first on a bumpy street course will clutch on the downshifts to avoid wheelhop. That was in a formula car with a sequential box.

Shifter karts are probably much more sensitive to locking the rear tires during a downshift than a Cup Car is.  Shifter karts have no suspension to speak of, so they tend to lose grip and slide very easily with abrupt changes in torque applied to the rear tires.



#25 Ross Stonefeld

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Posted 26 October 2013 - 11:32

Yeah but a kart that isn't locking the rear under braking isn't being driven hard enough  :p



#26 Fat Boy

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Posted 28 October 2013 - 21:14

Shifter karts are probably much more sensitive to locking the rear tires during a downshift than a Cup Car is.  Shifter karts have no suspension to speak of, so they tend to lose grip and slide very easily with abrupt changes in torque applied to the rear tires.

It's not even close, a kart is not hard to deal with at all. A Cup car is probably the most difficult car to drive well on the planet. Something like an F1 car actually does what you want it to do. A Cup car is a case-study in frustration.

 

Once you lock the rear tires on a stock car, that big rear axle starts jumping all around and then you are in real trouble.



#27 MatsNorway

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Posted 30 October 2013 - 16:44

It sure does not look like it given that F1 drivers and others who test them tend to do some minor slides/powerdrifts quite fast. I do not remember ever hearing about that from rookies in F1 cars.



#28 Ross Stonefeld

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Posted 30 October 2013 - 17:04

Oh spinning the rears is NASCAR 101, locking the rears is game over unless you're sliding into your pitstall. And even then it will probably get ugly.



#29 DogEarred

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Posted 31 October 2013 - 07:51

I think an F2000 is an H-pattern, so really does need a blip.

 

Plus maybe it needs it because it's a slightly different engine than a shifter kart?

 

Though I knew guys who raced British Formula Ford back when it was an elite series, and they looked at me like I was speaking Latin when I talked about clutches. 

 

Yes you're right. I always used the clutch for up & down shift. Upshifts, if done with a bit of finess (one fingered), would probably lose you no time at all compared with 'crashing' the gearchange.

For downshifts, I used quite high amounts of 'blips', especially braking from high speed into slow corners. It allows better control on turn in & the engine braking effect allowed slightly less harsh & better contolled braking. If you judge it all correctly, you could turn in using the brake to help & smoothly transition to the throttle early. The engine revs were nearer where you wanted them to be also.

Also, I could never afford the money to go crashing gears.

 

The smooth way is fastest!



#30 Fat Boy

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Posted 31 October 2013 - 17:43

It sure does not look like it given that F1 drivers and others who test them tend to do some minor slides/powerdrifts quite fast. I do not remember ever hearing about that from rookies in F1 cars.

 

I'm not sure what you're saying, but here's the deal. On the power side of the corner, wheelspin is less of an issue than locking the rears under braking. Also, powerslides are not necessarily difficult. The trick is sliding it enough without sliding it too much. It's easy to slide it around and go slow. The bitch about stock cars is that you have to 'under-drive' the car without just plain going slow. It's freakin' _tough_.



#31 Fat Boy

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Posted 31 October 2013 - 17:50

Yes you're right. I always used the clutch for up & down shift. Upshifts, if done with a bit of finess (one fingered), would probably lose you no time at all compared with 'crashing' the gearchange.

For downshifts, I used quite high amounts of 'blips', especially braking from high speed into slow corners. It allows better control on turn in & the engine braking effect allowed slightly less harsh & better contolled braking. If you judge it all correctly, you could turn in using the brake to help & smoothly transition to the throttle early. The engine revs were nearer where you wanted them to be also.

Also, I could never afford the money to go crashing gears.

 

The smooth way is fastest!

 

 

You can not use the clutch and still be smooth. In fact, I'd argue that it makes you be smoother and it definitely allows you to be faster. It's not necessary to have 'big' blips when downshifting. It's necessary to have appropriately sized and timed blips. There's a difference.

 

The ultimate extention of what I'm talking about is electronic shifters on Indycars/sportscars. They are used on conventional (albeit sequential, though that doesn't matter) gearboxes and they work great. Shift times are measured in milliseconds(well, on the order of 50-100 of them) and the gears car run a 24 hour race and come out looking perfect. It's impressive as hell.


Edited by Fat Boy, 31 October 2013 - 17:50.


#32 jpf

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Posted 31 October 2013 - 19:35

Fat Boy, are those indy/sportscar gearboxes then just cutting spark and using a hydraulic actuator to move the barrel?  That's like the pre-seamless F1 gearbox days, no?



#33 Fat Boy

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Posted 31 October 2013 - 21:42

The engines have timing/spark cut and the gearbox is shifted by a pnuematic actuator. The throttle blippers are also pnuematic.



#34 bigleagueslider

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Posted 01 November 2013 - 03:26

Shifter karts are much different than most any type of single seat formula car, sports car or stock car.  Shifter karts mostly use 2-stroke engines, have no suspension to speak of, and have no rear end differential.  If you've ever seen a shifter kart race, you'd have noted that the karts do quite a bit of sliding when braking and cornering.  And with highly-tuned 2-stroke engines it is critical to keep the engine rpm within its very narrow usable power band when braking/downshifting.

 

Driving a high-performance shifter kart (like a superkart) is very physical.  The lack of suspension, low vehicle mass/inertia, very direct reponse to steering inputs, and high ratios of power/braking-to-weight provide an excellent way to sharpen driving skills.