Car Weight Vs Tyre Width

[GTS-t VSPEC]

Hi guys,

Currently looking into running my car in Street Car Competition here in WA, which run primarily under the Group 3D - Sports Sedan rules.

They provide a table of minimum race weight versus displacement and tyre width. After peoples experience as to whether it would be better to have 100kg less weight or 1" wider rims.

The car is 2.6L, and with the turbo multiplier sits in the <4.5L displacement. So with 8" rims minimum weight is 1250kgs, or 9" rims is 1350kgs.

The tyre is a control tyre, Bridgestone RE55.

Cheers

Paul

[istdercollen]

I would definitely just take the 100kg less. especially on a nice tire like the RE55

[unique1]

i assume it would depend on power output as to how much traction you may sacrifice going the smaller diameter. Will be keen to see how it would go in the racing.

[Duncan]

Well....can you get the car down to 1250?

The table you have posted is interesting...there is no tyre width limit based on weight in the cams rules so they are a local addition. They are very restrictive so it will be interesting for the competition.

The best thing to do is to have a look at the front running cars (or those you want to be competitive with), what do they weigh?

Also have a good look at available sizes and prices before you decide....presumably dunlop slicks are the ones to have, they are here.

[Risking]

That's actually a really interesting rule.like Duncan said it certainly would wake up the competition. You need a light car that looks after it's tires well.

I'd try and get it into the 1250kg 8 inch rim category. The extra inch or rim width is only going to help with corner speed something that can be had with well sorted suspension as opposed to slower acceleration and straight line speed which requires more power and possibly less reliability.

Do you know what the car weighs?

[BezerkR32]

WHAT CAR IS IT.......NOT MANY STREET CARS ARE CLOSE TO 1250KG.

[GTS-t VSPEC]

WHAT CAR IS IT.......NOT MANY STREET CARS ARE CLOSE TO 1250KG.

Although it's Street Car you can strip out pretty much everything, aslong as you retain the standard bodyshape. Can replace the windows with Lexan, replace bonnet, fenders and boot with CF or fibreglass.

It's an R33 GTS-t, so not sure my chances of getting it down to 1250kg even if I stripped out everything. Currently in the process of removing sound deadening and wiring harness etc.

The front running cars tend to be the Rotaries, even with there additional penalties applied.

Unique1, The car is running 500rwhp at the moment, and has traction issues even with the the 9" tyres at the moment.

Risking, The car weighted 1370kg before serious weight reduction, and that was with an extra passenger seat, so I'd imagine we could get somewhat close to 1250kg, but not all the way there. Then I'd have the option of running at 1250+, or adding back in the weight where I want it, to make it back up to 1350kg.

Duncan, Not Dunlop slicks, Bridgestone RE55s are the control tyre.

[Ant97GTR]

Personally I would go the 100kg less....1" more rim is not enough to outweigh (hahaha) the 100kg advantage IMO.

Knowing all about your traction issues I would look at sorting suspension and power delivery in order to improve in this area.

[GTS-t VSPEC]

Personally I would go the 100kg less....1" more rim is not enough to outweigh (hahaha) the 100kg advantage IMO.

Knowing all about your traction issues I would look at sorting suspension and power delivery in order to improve in this area.

Hi Ant,

We have improved the suspension from the last time you've seen it, and changed turb to improve the power delivery too. Thinking of going with E85, so I can improve the mid-range, and reduce the top-end power a bit, in order to maintain a bit better traction.

[Ant97GTR]

Hi Ant,

We have improved the suspension from the last time you've seen it, and changed turb to improve the power delivery too. Thinking of going with E85, so I can improve the mid-range, and reduce the top-end power a bit, in order to maintain a bit better traction.

I remember you telling me that you changed the turbo but didn't know about the suspension.....I will assume that you went adjustable everything and can now setup the car properly.

Perhaps people with more track day experience running high HP rwd cars can advise further but it will come down to balancing the power with the delivery in order to get traction with the set rim width. Your suspension may need a few tweaks as well. I know that Adz's rwd 32 just pumped out an amazing time at Sandown but he is running much wider wheels than 8-9" and for the most part it was down to suspension settings.

[GTS-t VSPEC]

This is the car as it was at Dutton 2008 for those who haven't seen it.

[GTS-t VSPEC]

I remember you telling me that you changed the turbo but didn't know about the suspension.....I will assume that you went adjustable everything and can now setup the car properly.

Perhaps people with more track day experience running high HP rwd cars can advise further but it will come down to balancing the power with the delivery in order to get traction with the set rim width. Your suspension may need a few tweaks as well. I know that Adz's rwd 32 just pumped out an amazing time at Sandown but he is running much wider wheels than 8-9" and for the most part it was down to suspension settings.

Yep, went from the TO4Z down to a 3076R.

We've spent time tweaking the suspension, but everytime we change tyre brands we seem to go back to square one. At least with a control tyre we'll have the time to keep tweaking small improvements out.