9 replies to this topic

[Thrasher]

I don't know much about suspension design so I figured this was the best place to ask.

Why do touring cars like in the BTCC or DTM seem so bouncy? It's not a very violent bouncing but they seem to get quite a good bit of air under the tire(s) when they go over the curbs and when they land you can see them still rocking up and down, especially the back end. But the bounce seems like it is very firm. Does this make any sense? I also think this was much more noticeable in the touring car races around the 1980's.

I also notice a similar of bounciness motion (allthough to a lesser degree) in the tuned up Honda civics or other import "ricers" as many people call them. You can see them sort of bouncing a little bit as the slow down and go over speed bumps/humps.

[Crafty]

The touring cars bounce for a couple of reasons.. the drivers are typically very aggressive over big kerbs, the other is that they are very stiffly spring to reduce body roll, they want ot try and keep the cog down the middle of the car.

The street cars that you've seen bouncing is because the owner has lowered the car using shorter springs, as a result they have less travel, so have to be stiffer. I've seen plenty of street cars that are virtually coil bound (i.e. theres hardly any movement in the spring), leaving the car to bounce on the bumpstops.. they think it makes their car handle like a touring car, everyone else thinks its bl**dy uncomfortable...

[Lukin]

I don't really agree with the second bit of that first paragraph. Touring cars aren't setup anywhere near as stiff as an open wheeler in terms of wheel rate. If they were launching off the kerbs would make them horribly unstable. Most touring cars are designed so that grip from downforce isn't the dominatring factor. As a result the cars can be run much softer than open wheelers which allows them to be more aggressive. Also, don't forget most TC series run control tyres which sometimes require softer setups to get the best out of them.

[shaun979]

I haven't watched touring car racing for a while, but in 90's BTCC racing, I recall seeing rims that seemed slightly wider than the tire. What was the reason for this? Keeping the tire profile more square?

[Ray Bell]

Originally posted by Crafty
The touring cars bounce for a couple of reasons.. the drivers are typically very aggressive over big kerbs, the other is that they are very stiffly spring to reduce body roll, they want ot try and keep the cog down the middle of the car.....

Two things here...

The 'aggressive' driving of these cars over the kerbs is because they respond to it with reduced lap times. If a Formula 1 car benefitted by jumping kerbs, all F1 drivers would be similarly 'aggressive'.

And what do you mean 'keep the cog'?

The street cars that you've seen bouncing is because the owner has lowered the car using shorter springs, as a result they have less travel, so have to be stiffer. I've seen plenty of street cars that are virtually coil bound (i.e. theres hardly any movement in the spring), leaving the car to bounce on the bumpstops.....

Agree completely with the discomfort factor...

But the meaning of the term 'coil bound' is better defined by saying that the coils completely close up, so that there is no movement left at all. Bump stops sometimes prevent that happening, of course, but if a spring were to be coil bound, then it might not even reach the bump stops.

The laugh is those, by the way, who lower road cars too much and then have to drive their 'ricers' into shopping centres and other carparks where there are speed humps. Passengers alight to give extra clearance, they walk on as the driver attacks the speed humps at an angle... agitated folk in normal cars follow and curse... good fun!

[Calorus]

Originally posted by Ray Bell


Two things here...

The 'aggressive' driving of these cars over the kerbs is because they respond to it with reduced lap times. If a Formula 1 car benefitted by jumping kerbs, all F1 drivers would be similarly 'aggressive'.

And what do you mean 'keep the cog'?

They can and do - recommend close attention at Magny Cours.

'cog' should read 'CoG' i.e. Centre of Gravity but the DTMs especially, but the Super Tourers and Super 2000 all go to some quite extreme extents to move all of the mass onto the Centre of Gravity in the middle of the car.

Originally posted by Ray Bell


Agree completely with the discomfort factor...

But the meaning of the term 'coil bound' is better defined by saying that the coils completely close up, so that there is no movement left at all. Bump stops sometimes prevent that happening, of course, but if a spring were to be coil bound, then it might not even reach the bump stops.

The laugh is those, by the way, who lower road cars too much and then have to drive their 'ricers' into shopping centres and other carparks where there are speed humps. Passengers alight to give extra clearance, they walk on as the driver attacks the speed humps at an angle... agitated folk in normal cars follow and curse... good fun!

Discomfort is a relative thing. I'd actually argue that it's worse to try to push a blancmange hard, than to suffer the odd pot hole pottering about in a well sorted car.

And if you turn up at the Bomb Hole full pelt with factory suspension. you'll be going home at best in a taxi, and at worse in an ambulance.

Personally I'm a solemn believer in horses for courses and withthe quality of roads I'm faced; these Teins suit me down to the ground - theoretically I could change the settings back to something a touch less 'keen', but I'd only succeed in a crappy and pointless compromise before having to try to work out where everything was next Snetterton.

[Canuck]

Originally posted by Calorus

Personally I'm a solemn believer in horses for courses and withthe quality of roads I'm faced; these Teins suit me down to the ground - theoretically I could change the settings back to something a touch less 'keen', but I'd only succeed in a crappy and pointless compromise before having to try to work out where everything was next Snetterton.

Uhm...what?

[toe-out]

He likes stiff lowered car, not Camry like boating.

[sportyaccordy]

My car is lowered about 3" on stock shocks *cue collective vomiting* but it doesn't at all ride rough. The front springs are stiffer than stock but the rears are maybe 10% stiffer, and it's fine. I actually want to see how my car handles bumps from an outside perspective...

[Greg Locock]

"Any suspension will work if you don't let it move" paraphrase of C Chapman.