Best way to improve handling

[Muttley]

In this thread:

http://www.seatcupra.net/forums/showthread.php?t=258200


DPJ wrote
To quote **** Shine

There are two critical geometric points to consider when discussing suspension performance: the center of gravity, and the roll center. The distance between these two points (the roll moment arm) determines the tendency of the car to roll.

The center of gravity moves with the ride height of the car. Lowering the car one inch will drop the center of gravity approximately eight tenths of an inch (only the sprung portion of the weight moves downward). The location of the roll center is a function of the suspension geometry. Lowering the body one inch on a Mk4 VW lowers the roll center approximately one and a half inches.

As a result of lowering the car 1 inch, the roll moment arm has increased more than half an inch, making it much easier for the car to roll.

When a car is allowed to roll, the resulting weight transfer decreases the available grip and keeps the car from handling to its potential.​

As I understand it, the downward sloping wishbones you'll get with a lowered LC will give a much lowered roll centre.


Willie wrote
For those that don't recognize the name **** Shine he's the man when it comes to setting up the suspension on the MK4 Golf GTI.
He posts alot on VW Vortex, if you haven't been on this site....what you playting at.....get your ass on there and get searching, and know his stuff.

when setting up for the best handling on a MK4 Golf GTI, same set up as the LC, he actually raises the ride height of the front of the car, lowers the rear and fits a 28mm rear ARB. It doesn't look pretty but handles very well on the track.

 

[caribe]

Thanks for that, I have a rear ARB ordered as well.

My racing and track days are behind me for now (especially as I sold my race car :-(

So this is just a pure road car, just looking to tighten things up a bit.

 

[8bit]

If you're looking to tighten it up a bit then go easy on the drop, get the ARB on and get some poly bushes fitted while the coilovers are getting fitted. The bushes will make for a slightly harsher ride however but if you've bought decent coilovers then this will balance out a little.

 

[caribe]

Its not going down far.

I need the car to be a daily driver on some less than pleasant roads.

Looking like a 35 mm drop after speaking to my garage

 

[8bit]

Also get some LCR topmounts for when the coils get fitted. Two reasons for this - one is that they're more solid so you'll get sharper turn-in. The other is that from what I've seen they're flatter than most other mk4 platform cars topmounts. This means that you'll get the first 5 - 10mm of the drop from those, meaning you don't need to wind down the coilies as much. That in turn means longer suspension travel available and less pre-compression on the springs.

Also get proper 4-wheel alignment and geometry done after fitting the suspension, that made a significant difference on my car.

 

[caribe]

Also get some LCR topmounts for when the coils get fitted. Two reasons for this - one is that they're more solid so you'll get sharper turn-in. The other is that from what I've seen they're flatter than most other mk4 platform cars topmounts. This means that you'll get the first 5 - 10mm of the drop from those, meaning you don't need to wind down the coilies as much. That in turn means longer suspension travel available and less pre-compression on the springs.

Also get proper 4-wheel alignment and geometry done after fitting the suspension, that made a significant difference on my car.

Thanks very much for the advice.

Spoke to the guy fitting them and he mentioned the top mounts as well.

Car is going in tomorrow night so will be picking it up on Thursday .... Heopefully be a nicer driver after that.

Will get some pics up as well

 

[8bit]

Fingers crossed, sounds like you're going about it the right way for handling. Post back with how you find it and remember, once the coils are fitted it might not look like its' dropped much but the springs will settle over a few drives/couple of weeks.

What coilies did you go for, out of interest?

 

[caribe]

Pictures were before and after a polish lol

Will post pics once the suspension goes on.

 

[501UKAutoCare]

some lightly stiffer progressive springs should help, and as others mentioned, Thicker Rear ARB is a good shout.

 

[caribe]

Car is in garage now getting the coilovers fitted tonight and then set up tomorrow. Garage looking to bring it down about 40 -45 mm so will see what it looks like. Will post pics the morns night

 

[BenG]

Amen to that, my 16's feel about half the weight of my 17's. Although the 17's do drive a lot better despite the extra weight.

Recently put 16s on my FR TDI, with narrower tyres (205/55 vs. 225/45), saving 4.2kg a corner - the standard 17s + tyres were 21kg each!

It's taken the choppy edge off the ride, reduced the tyre noise a bit and the car still turns in and grips well with half-decent tyres (Goodyear SP Sport).

 

[BenG]

Recently put 16s on my FR TDI, with narrower tyres (205/55 vs. 225/45), saving 4.2kg a corner - the standard 17s + tyres were 21kg each!

It's taken the choppy edge off the ride, reduced the tyre noise a bit and the car still turns in and grips well with half-decent tyres (Goodyear SP Sport).

Incidentally, I lowered two of my previous cars and while it did improve the handling, I got cheesed off with being bounced around by our lousy UK road surfaces, so I think the uprated anti-roll bar route is a good way to go to avoid screwing up the ride quality too much, considering the Leon is not exactly a comfortable ride to start with...

 

[edewer]

Out of interest, what are peoples thoughts on running a set of slightly better springs from the likes of Eibach or H&R on standard dampers? As surely unless you're going to go for the likes of KW V3s or top end stuff then the adjustable side of things in really for looks?

Having had coilovers before on other cars, yeah theyre great, but are they really that necessary if you dont have full damping and rebound adjustment!

 

[caribe]

Just back from the garage.

Had all the tracking done and the suspension has been set correct to the MM.

Also replaced the tyres at the same time and the discs and pads.

New ARB will go on soon but its not here so will go in next month to get that done when the car goes back to check the suspension after 500 miles.

Drove it on the A1 and a few country roads and it seems better now.

I am pleased with it

 

[d1n93r]

that looks well. take a look into upper and lower strut braces. im running eibach pro kit lowering 30. whiteline 24mm rear arb and the upper and lower braces. handles great

 

[caribe]

Will be getting the ARB sorted as well as getting the upper braces done... just need to finish paying for the wedding first lol.

It does look loads better now. Was going to get a front splitter but don't think it will get over any bumps at all ignorant I do that.

 

[BenG]

In this thread:

http://www.seatcupra.net/forums/showthread.php?t=258200


DPJ wrote
To quote **** Shine

There are two critical geometric points to consider when discussing suspension performance: the center of gravity, and the roll center. The distance between these two points (the roll moment arm) determines the tendency of the car to roll.

The center of gravity moves with the ride height of the car. Lowering the car one inch will drop the center of gravity approximately eight tenths of an inch (only the sprung portion of the weight moves downward). The location of the roll center is a function of the suspension geometry. Lowering the body one inch on a Mk4 VW lowers the roll center approximately one and a half inches.

As a result of lowering the car 1 inch, the roll moment arm has increased more than half an inch, making it much easier for the car to roll.

When a car is allowed to roll, the resulting weight transfer decreases the available grip and keeps the car from handling to its potential.​

As I understand it, the downward sloping wishbones you'll get with a lowered LC will give a much lowered roll centre.


Willie wrote
For those that don't recognize the name **** Shine he's the man when it comes to setting up the suspension on the MK4 Golf GTI.
He posts alot on VW Vortex, if you haven't been on this site....what you playting at.....get your ass on there and get searching, and know his stuff.

when setting up for the best handling on a MK4 Golf GTI, same set up as the LC, he actually raises the ride height of the front of the car, lowers the rear and fits a 28mm rear ARB. It doesn't look pretty but handles very well on the track.

That's interesting. If the roll centre's below the C-of-G rather than above it, does that affect the direction of roll? I guess it can't, as the car will still lean towards the outside of the bend

I gather Seat lowered the FR model compared to the usual S/SE spec, and the Cupra R further, and I assume they wouldn't have done so if that would have worsened the body roll?

I guess raising or lowering one end of the car more than the other would affect the steering kingpin angle and so the weight and self-centering of the steering as well as the camber change introduced by steering angle.

 

[Muttley]

Typically the roll center is below the CofG for purely mechanical reasons - large parts of the weight of the car (engine, people) are high up, and the roll center is low, set by the suspension attachment points and its geometry - I found a useful set of diagrams here, I'm sure there are others.

If you could contrive a car with the roll center above the CofG then it would lean in the opposite direction to what we're used to, like a motorcycle, you'd lean inwards on turns. There would still be weight transfer, though, which is undesirable: the roll center is usually set as close as possible to the CofG to give neutral roll, allowing each corner to contribute maximum grip in turns.

My Toledo TDI 150 Sport has the Sports suspension which is 15mm lower than the ordinary (Comfort) suspension package, but also has stiffer springs and damping and heavier roll bars. If the geometry is unchanged ( and I'm almost certain it is ) then the roll center-to-CofG separation is increased by this, making the roll moment larger i.e. making it more inclined to roll. This is controlled by the stiffer setup, and includes different dampers for full, properly damped, travel. The Sport setup is driven partly by looks, of course, which dictate a lower setting - and the car is not sold as a track car, so ultimate track handling is compromised by the need to look sporty using a Mk.4 Golf platform. Overall I have to say it's done well, the feel of the Sports package is much better than the Comfort suspension I had on my old TDI 110. I have no idea how much better it is in terms of absolute grip around corners though, I very rarely push towards those limits. On public roads it's almost never justifiable, and I haven't taken the car on a track day or skid pan.

The Cupra R has different front suspension, taken from either the Audi TT or the S3 I think, and is 20mm lower than standard as far as I recall. Rear suspension is different too. The Cupra R is an exotic beast compared to the rest of the range, a "racing" hatchback and the suspension changes are made to go with that image.

The rear roll center is already higher than the front one, resulting in a tilted roll axis, like nearly all road cars. Small differences in lowering between front and back will make small changes to the steering feel, but not outrageous ones, and nothing that can't be handled with the obligatory power steering.

Honestly, the one thing I miss most from my old Mk.1 Golf GTI is the unpowered steering - you could feel what was going on at the front wheels so much more easily.

 

[BenG]

Interesting info! It seems like the first things people do when modifying is fit bigger wheels and lower the car, usually for looks, which not only messes up the ride quality but possibly also the handling, requiring stiffer springs to maintain the same degree of body roll. I guess uprated ARBs would be a way to improve the handling without the same effect on ride or cround clearance, but the bars on the FR are already pretty large (23 or 25mm front - unsure about rear).

I'd wondered if the standard suspension would be much more comfortable than the sports version, but even my FR doesn't handle that well and rolls and understeers quite a lot in corners, so I guess the S/SE suspension would just be worse. Also I agree with you that the steering is too light - much more so than my old Focus Mk 1 so little feel...

 

[traumapat]

when setting up for the best handling on a MK4 Golf GTI, same set up as the LC, he actually raises the ride height of the front of the car, lowers the rear and fits a 28mm rear ARB. It doesn't look pretty but handles very well on the track.

Thats very similar to the orignal advice given to me by jabbasport. I suggested strut bracing and upgrading the front ARB and was told to just go with a thick rear arb.. i think mine is 28mm.
It was suggested that increasing the rigidity of the front of the car could increase understeer.

I would imagine raising the front of the car would involve the rear arb even further.