Hi guys, I was recently working on adding to the mod list of my MK2 Octavia VRS estate, and was considering offset sidewall profiles front and rear.

 

Basically I wanted to run 17s on the front and 18s on the rear while maintaining the same outer tire diameter on both in order to hopefully improve corner exiting traction, straight line grip and help settle the car while accelerating on rough roads.

Would the bigger sidewall on the front help with this, and does anyone have any experience with how it would affect handling?

I'd assume it would somewhat help to neutralize the understeer as the front would get more grip while cornering?

 

Other mods include front and rear ARBs, lowering springs, anti lift kit and uprated callipers.

 

Any helps or general input is appreciated 

You plan to use a combination like 225/45/17 - 225/35/18?

 

Wacky races springs to mind!

 

I can only imagine how it would affect handling but I'm confident your insurance provider would want to know and it'd probably not pass an MOT.

 

Consider run flat or extra load rated tyres for a stiffer sidewall.

1 hour ago, MicMac said:

You plan to use a combination like 225/45/17 - 225/35/18?

 

Wacky races springs to mind!

 

I can only imagine how it would affect handling but I'm confident your insurance provider would want to know and it'd probably not pass an MOT.

 

Consider run flat or extra load rated tyres for a stiffer sidewall.

So the idea is to have a larger softer sidewall on the front in order to get better traction, obviously I'd declare it to the insurance just like all my other mods, I'm with Adrian flux and their usually pretty relaxed about changed. I haven't had more than a £30 admin fee for anything so far.

 

Not sure that this change would do what you want - I suspect the taller front sidewalls will just induce more understeer.

46 minutes ago, Warrior193 said:

Not sure that this change would do what you want - I suspect the taller front sidewalls will just induce more understeer.

I'm more interested in the affect on traction while accelerating, at the moment with the 18s and as it has an open diff, any imperfections in the road while accelerating cause the car to get unsettled, torque steer and loose traction. 

 

My hope was that the larger sidewall would let the tire flex more and create a larger contact patch, which would help it deal with dirt and imperfections on the road a little better. 

 

I'm basing this off the same theory as the massive sidewalls on say a drag setup or a rally tire, which let the tire flex more and stretch it's contact patch across the road better. 

 

Again, this is more of a brainstorming idea than something I'm immediately planning to do to my car. I'm just interested in everyone's take on the subject. 

Just try dropping the pressure in the fronts and see how it goes.

1 hour ago, MicMac said:

Just try dropping the pressure in the fronts and see how it goes.

The issue with that is the already bad travel on the 18s sidewall. If I drop the pressure further and hit a bad bump or pothole, the sidewall will likely bottom out into the rim and crack or warp it. The allure of the 17s is the extra sidewall travel without having to sacrifice tire pressure.

Hi.

If you do ever need any help with insurance at all then please feel free to drop me a line.

Regards,

Dan.

1 hour ago, EscapingPiston said:

The issue with that is the already bad travel on the 18s sidewall. If I drop the pressure further and hit a bad bump or pothole, the sidewall will likely bottom out into the rim and crack or warp it. The allure of the 17s is the extra sidewall travel without having to sacrifice tire pressure.

There's only 1.27 cm difference,  225/45/17s are not great on UK public roads.

 

Get a set of 16s from a scrappy and expect a wallowy ride.

 

I suspect a track tuner would suggest suspension upgrading before changing wheel/tyre sizes.

1 hour ago, DAN@ADRIAN FLUX said:

Hi.

If you do ever need any help with insurance at all then please feel free to drop me a line.

Regards,

Dan.

These guys are the bomb 👌

34 minutes ago, MicMac said:

There's only 1.27 cm difference,  225/45/17s are not great on UK public roads.

 

Get a set of 16s from a scrappy and expect a wallowy ride.

 

I suspect a track tuner would suggest suspension upgrading before changing wheel/tyre sizes.

Fair enough, what about straight-line traction? I assume the grip will be increased at the cost of soft wallowy cornering

I can't imagine any change in grip by changing sidewall height.

I would say straight line traction is more of a tyre compound issue.

 

Bear in mind a FWD car places different loads on its driving tyres compared to a RWD dragster.

 

Where a RWD will tend to load the tyres and exhibit rear squat as the weight transfers rearwards during acceleration a FWD will go light up front and rise.

 

I think you are applying off-road grip practices to public road situations where snow would be a valid exception.

 

Having reread your initial post and noted the rough road comment I think 16s and a set of rally tyres may be the answer, check out some rally wheel/tyre specs just for size comparison.

6 hours ago, MicMac said:

I would say straight line traction is more of a tyre compound issue.

 

Bear in mind a FWD car places different loads on its driving tyres compared to a RWD dragster.

 

Where a RWD will tend to load the tyres and exhibit rear squat as the weight transfers rearwards during acceleration a FWD will go light up front and rise.

 

I think you are applying off-road grip practices to public road situations where snow would be a valid exception.

 

Having reread your initial post and noted the rough road comment I think 16s and a set of rally tyres may be the answer, check out some rally wheel/tyre specs just for size comparison.

I'll have a look, cheers!

On 23/09/2020 at 11:18, EscapingPiston said:

Basically I wanted to run 17s on the front and 18s on the rear while maintaining the same outer tire diameter on both in order to hopefully improve corner exiting traction, straight line grip and help settle the car while accelerating on rough roads.

Would the bigger sidewall on the front help with this, and does anyone have any experience with how it would affect handling?

I'd assume it would somewhat help to neutralize the understeer as the front would get more grip while cornering.

 

 

Firstly, I wouldn't be adventurous enough to try it on a road car, at least one I hadn't tried pretty thoroughly by throwing it about on a test track first. You'll probably say I just a bit too conservative, but keep in mind that's my opinion.

 

Secondly, you will probably find it does have a positive effect, but quite a limited one. On rough roads, if you have a real washboard surface, it will have an effect, but then the shocks are likely to have a much bigger effect (it would be much bigger, if you had complete freedom with shock settings, but with real world constraints, you almost certainly don't, so I'm removing the word 'much').

 

On 23/09/2020 at 11:18, EscapingPiston said:

Other mods include front and rear ARBs, lowering springs, anti lift kit and uprated callipers.

 

Here's the problem - while playing with the tyre sidewalls can help, it is difficult for it to help enough so that it can overcome the damage done by fitting a stiffer front ARB, and the lowering springs can have an effect too, if the spring rates aren't carefully chosen.

Other things like engine mounts also get involved, and there is a danger that, by the time you've finished, you are redesigning the entire suspension system.

On 24/09/2020 at 03:27, MicMac said:

I would say straight line traction is more of a tyre compound issue.

 

It can be, but it can also be something like engine mounts. If the engine moves or squirms around as you take off, that can be quite unpleasant.

 

Corner exit is almost certainly the well known 'in roll, one wheel gets decreased vertical load, and traction for that wheel rapidly decreases' issue. While that can be made worse by almost anything else, tyre compound is one of those issues (as are bound and rebound rates, wheel and tyre mass, effective spring rates, tyre pressure, engine mounts - basically anything, really),