4722 replies to this topic

[techieboy]

It may, or may not be the case that the Velise chassis might be better on the same sized tyres all round but if you have über wide tyres up front, it's going to be a pig to drive. It'll tramline everywhere and low speed manouverability will be interesting. Nearly all of that extra width is going to have to go outboard of the centreline of the existing wheel/tyre, assuming you want to be able to have any form of turning circle, and I'm not sure what impact that will have on wishbones etc, especially if you're planning on running low enough to worry a coke can.

[GeorgeBC]

You have got to get this car on track against other VX's Nev?! I cant wait to see the difference. When is your first trackday?

[Arno]

Yep and yep to those questions, a couple of inital pics and more details are on my website: https://sites.google.../07---update-24

BTW.. You may want to google a little (and perhaps talk to ChrisRandall) before choosing Image wheels.

It seems that they are in some cases somewhat too fragile. Several reports about wheels buckling/bending and such.

Perhaps a 'safer' path is to talk to the usual suspects on custom wheels like Compomotive, BRAID, etc. to see what they can do.

Bye, Arno.

[Nev]

Thanks for the tip Arno (and Luke by PM).

[steveboyslim]

It may, or may not be the case that the Velise chassis might be better on the same sized tyres all round but if you have über wide tyres up front, it's going to be a pig to drive. It'll tramline everywhere and low speed manouverability will be interesting. Nearly all of that extra width is going to have to go outboard of the centreline of the existing wheel/tyre, assuming you want to be able to have any form of turning circle, and I'm not sure what impact that will have on wishbones etc, especially if you're planning on running low enough to worry a coke can.

I would also be concerned abot wheel bearing load also.
Lotus redesigned the uprights with large wheel bearings for motorsport use, using large wheels with sticker tyres.

Steve

[Nev]

Nipper seems to be in a magazine...

[hairy]

Can I have an autographed copy?

[JimmyJamJerusalem]

I'm sure mr Borgman knows his stuff; I know Cliffie and Chris R speak VERY highly of him but you need extra width on your rear wheels due to them being the driven wheels which are therefore required to handle the torque (in your case excessive torque) so to say the fronts need to be the same width seems like a ludicrous point to make.... Did he explain why, and did you explain how wide you meant on the rears? What I'm thinking is mybe he thought 225's all round would work well (because it does!!). Not Naysaying Nev before you moan and call me a hypocrite (again ) just interested in what this guy has to say

[siztenboots]

pretty sure that laws of friction state the magnitude of the friction force is independent of the area of contact between the surfaces (for static and kinetic) the magnitude of kinetic friction is independent of speed of slippage

[Nev]

I'm sure mr Borgman knows his stuff; I know Cliffie and Chris R speak VERY highly of him but you need extra width on your rear wheels due to them being the driven wheels which are therefore required to handle the torque (in your case excessive torque) so to say the fronts need to be the same width seems like a ludicrous point to make....

Did he explain why, and did you explain how wide you meant on the rears? What I'm thinking is mybe he thought 225's all round would work well (because it does!!).

Not Naysaying Nev before you moan and call me a hypocrite (again ) just interested in what this guy has to say

I have to admit I was startled too. I dont think I impressed on him that I was thinking of 265mm or 275mm on the rears, so maybe he did think I was implying sticking 225 on both front and rear. We talked about so much for so long I can't remember all the details unfortunately, maybe I even misunderstood him or the context.

Before I buy my wheels I have to contact Chris Randal anyway as he will be doing the geo and recommending the change of suspension. At this point I will go through the wheel size/width options with him and Sam and maybe some others.

Just looking at similar mid engined RWD drive cars like Nobles, Porsches etc, they all seem to run approx 235 on the fronts and 275 on the rears. Then if you move up a notch to Ultimas etc it increases to 275 Front/335 rears etc etc, so the ratios stay the same. I would imagine our cars would need to follow the same principles.

Edited by Nev, 20 January 2012 - 04:25 PM.

[Nev]

Wow, just checked Google Analytics for the first time in ages, my website has had:

18,010 Visits

8,395 Unique Visitors

84,408 Page views

4.69 Pages/Visit

00:04:56 Avg. Time on Site

46.80% Bounce Rate

45.67% % New Visits

Edited by Nev, 20 January 2012 - 04:30 PM.

[cnrandall]

I'm sure mr Borgman knows his stuff; I know Cliffie and Chris R speak VERY highly of him but you need extra width on your rear wheels due to them being the driven wheels which are therefore required to handle the torque (in your case excessive torque) so to say the fronts need to be the same width seems like a ludicrous point to make....

Did he explain why, and did you explain how wide you meant on the rears? What I'm thinking is mybe he thought 225's all round would work well (because it does!!).

Not Naysaying Nev before you moan and call me a hypocrite (again ) just interested in what this guy has to say

I have to admit I was startled too. I dont think I impressed on him that I was thinking of 265mm or 275mm on the rears, so maybe he did think I was implying sticking 225 on both front and rear. We talked about so much for so long I can't remember all the details unfortunately, maybe I even misunderstood him or the context.

Before I buy my wheels I have to contact Chris Randal anyway as he will be doing the geo and recommending the change of suspension. At this point I will go through the wheel size/width options with him and Sam and maybe some others.

Just looking at similar mid engined RWD drive cars like Nobles, Porsches etc, they all seem to run approx 235 on the fronts and 275 on the rears. Then if you move up a notch to Ultimas etc it increases to 275 Front/335 rears etc etc, so the ratios stay the same. I would imagine our cars would need to follow the same principles.

Sam has some pretty sound theory (and he may well be correct) behind his thoughts ref the same size tyres front and rear but my view is something different. I would choose tyre size in relation to the amount of load the tyre will see and a high power, rear engine VX will have far more load on the back and need a bigger tyre to remain balanced. More tyre will give you more grip but you will be limited and compromised by any increase on rolling diameter as our cars are designed around relatively small wheels and tall ride heights. Its easy to push the roll centre of the car through the floor by running low on ride height and tall on tyres and any gains in mechanical grip will be eroded by instability and this is why guys like me move the hub centres to alleviate suspension geometry problems.

[Nev]

I think both you and Martynas (who has the Latvian race car (and whom I bought the clam off)) have put different wishbones and hubs on. I first have to let my bodyshop friend get the body in place before I even have an exact idea of what wheels/tyres will even fit in there yet. Thanks for your input Chris, will contact you once I have got to this point.

[ChrisS1]

Perhaps the ratio difference is due to the load on tyres front and rear and therefore the heat generated in the tyre. I.e same size front and rear on a RWD could result in warmer rears than front therefore poor cornering. Narrowing the front tyre results in less load being required to get the tyre to the same operating temp as the rear.

[Nev]

Indeed, I am sure you have a good point there Chris. Approx 65% of the car's weight is over the rear axle. On that basis the fronts should be 45%.

[chrisgold]

Go for 275 Front/335 rears

[Nev]

Go for 275 Front/335 rears

That would never fit under the clam.

Though those sizes sound laughable, the Ultima I drove was deffo the most planted car I have ever driven (by a big margin). At the time of test driving it, my normal run around was a Scooby and the difference in road handling was massive. I even remember remarking to Ted Marlow that the Ultima (with those wheel sizes) made my scooby feel "like I was driving a sponge" in comparison.

[Duncan VXR]

My Nitrons have been sent off for a service finally. I may re-spring them when I get the car geo-ed, depending on advice I get at the time. I think I will need stiffer springs, as my upper rear suspension wishbones show marks where they have bottomed out against the chassis with all the torque (!).

For information the wishbones fouling the chassis and getting the nice dent is not power related but just the suspension bottoming out and seen it on all power levels including std. Def agree on beefing it up though Nev with the higher power levels you are running and found doing this on my old one helped with controling my need for aggressive launches

Sounds like you are busy busy busy with the car - interested to see the ouput of the increased tyre plans

DG

[JG]

pretty sure that laws of friction state the magnitude of the friction force is independent of the area of contact between the surfaces (for static and kinetic) the magnitude of kinetic friction is independent of speed of slippage

Wrong.

Table 3 here lists most of the variables.
http://www.brachengi...lslipmodel1.pdf

[siztenboots]

an interesting set of proposals, but no actual proof

to resurrect some tyre sizes information from a while ago to consider will they fit under the clams or rub the chassis legs ( the links to actual dimension is of real note )

in terms of tyre availability in semi slick, the widest I can see fitting a VX is 255 staying with a 17" rim and thats with a 40 profile, and smallest rim width on that is a 8.5J , tread width is 232* , section width is 260* (varies by make), of course happy to be proven wrong.

I've looked and Bridgestone have removed the data for RE040, so can't get the width data. But a quick calculation came out at having ET20 for the 8,5J wheel

A more sensible compromise is the 235/40/17, tw=216*, sw=238* , which will go on a 8J rim.

given the difficulties a number of us have experienced getting tyres fitted to a 7.5J , this is one of the reasons why I prefer 8J minimum

I've avoided going to larger wheels sizes to the bad effects on the wishbone angles and bearings and the need to change suspension setups. If I was to change, I'd go to 15" all round, like Meldert did.

*sizes given from manufacturer data for Federal RS-R

tyre weights if anyones interested in total USM , plus actual sizes versus nominal sizes
RS-R , 8mm tread depth (http://www.federalti...c/spec595RS.pdf)
225/45/17 = 11.2kg , tw=206, sw=230
235/40/17 = 11.5kg , tw=216, sw=238
255/40/17 = 12.4kg , tw=232, sw=260 (8.5J)

R888 , 5mm tread depth (http://www.racetire....s/toyo_r888.htm)
225/45/17 = 10.9kg , tw=221, sw=231
235/40/17 = 10.9kg , tw=238, sw=243
245/40/17 = 11.4kg , tw=238, sw=249
255/40/17 = 11.8kg , tw=259, sw=264 (8.5J)
315/35/17 = 13.6kg , tw=300, sw=320 (the MaxR super wide option! , 11J rim needed)

There are other alternatives, like the Kumho V70a, goes upto 275/40 for an almost sensible price.