SCCA F-Street Setup. What's Everyone Done so Far?

[jdub.csu]

I used a 5mm spacer as well but not because of tire clearance issues. I used them to help widen the front track to balance out some of the 1.7" wider rear track. What "help" this has is probably minimal but it makes me feel better! ;)

I feel like this is the case for a lot of the mods we do on these cars

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[rodhx]

I've been through much of this thread and saw folks kicking around the idea of using 18s instead of 19s for autocross. Did anyone actually try it? Specifically I have a EBPP so now DStreet.

Bridgestone also has a 265/40-19 RE71R. I'm guessing the slight gearing help doesn't offset the loss of tire width though.

 

[jdub.csu]

I've been through much of this thread and saw folks kicking around the idea of using 18s instead of 19s for autocross. Did anyone actually try it? Specifically I have a EBPP so now DStreet.

Bridgestone also has a 265/40-19 RE71R. I'm guessing the slight gearing help doesn't offset the loss of tire width though.

I will only go to 18's once I have a blower and can lower the gearing so I get better top speed. Making it even shorter is just cruel punishment.

 

[kz]

I've been through much of this thread and saw folks kicking around the idea of using 18s instead of 19s for autocross. Did anyone actually try it? Specifically I have a EBPP so now DStreet.

Bridgestone also has a 265/40-19 RE71R. I'm guessing the slight gearing help doesn't offset the loss of tire width though.

I don't think anybody thought about 18s in street classes since it would make gearing even worse being restricted by wheel widths...

265/40 gives less than 1 mph difference at 60 mph compared to 285/35 so highly doubt anybody would go for significantly narrower tire... On most local courses 285 is enough, on national ones you're screwed either way... That applies to GT though, question is what's the max speed in 2nd for EB.

 

[SteveW]

Back before I had my own Mustang I was thinking 18s might work with the EB. My rationale was that the lower gearing would actually make 3rd work well with the engine's power band. However, I'm pretty much the poster boy around here for trying things that don't work so well so, there's that...

 

[rodhx]

Back before I had my own Mustang I was thinking 18s might work with the EB. My rationale was that the lower gearing would actually make 3rd work well with the engine's power band. However, I'm pretty much the poster boy around here for trying things that don't work so well so, there's that...

Thanks. Those are the discussions I was referring to. Looks like a 275/35-18 effectively changes the rear end ratio from 3.55 to 3.75. I don't know if that's enough to be worthwhile or simply be even more aggravation.

 

[SteveW]

If the courses you run on are slow (consistently less than 60 mph) then there may be advantages to 18s. If your focus is on national events I'd have to say don't shorten 2nd.

I made this chart a while ago. The GT should be changed to 6800.

 

[Norm Peterson]

Are those charts based on the actual tire revs per mile claimed by the tire mfr?


Norm

 

[rodhx]

That chart really helps. thank Steve

I was really intent on running the 275/40-18 version of the new Nexen since it is the same diameter as a 275/35-19 but allows a much lighter wheel. Found out after I've ordered the tires & bought wheels that the 275/40 is a "secret" drift compound and not like the rest of the SUR4G lineup. I say "secret" because there is nothing in the information published by Nexen or Tire Rack to let the consumer know that at least one of the sizes is not at all like the rest of the lineup. Of course my luck is such that the only size I'm interested in is the bad one.

 

[SteveW]

Are those charts based on the actual tire revs per mile claimed by the tire mfr?


Norm

I took the diameter from Tire Rack's spec pages and input that along with gear ratios and rpm here: http://www.apexgarage.com/tech/gear_ratios.shtml

 

[SteveW]

That chart really helps. thank Steve

I was really intent on running the 275/40-18 version of the new Nexen since it is the same diameter as a 275/35-19 but allows a much lighter wheel. Found out after I've ordered the tires & bought wheels that the 275/40 is a "secret" drift compound and not like the rest of the SUR4G lineup. I say "secret" because there is nothing in the information published by Nexen or Tire Rack to let the consumer know that at least one of the sizes is not at all like the rest of the lineup. Of course my luck is such that the only size I'm interested in is the bad one.

Sorry, man. I bought a suspension package about 2 yrs ago that I thought would be pretty good but am running into limitations with it. I also bought a set of one of the new compounds this year thinking they'd be a player but have found out I'm leaving a lot of time on course with them.

 

[rodhx]

This morning I was able to get the Nexen order canceled. Still got a nice light set of 18s I'm not sure what I'll do with. Might get some of the new Continentals ECS for them in that 275/40 size for daily & rain tires.

 

[Norm Peterson]

I took the diameter from Tire Rack's spec pages and input that along with gear ratios and rpm here: http://www.apexgarage.com/tech/gear_ratios.shtml

Does that calculator correct for 'effective rolling radius'? There's a slight difference from nominal rolling radius that comes from tire compliances and circumferential compression of the tire tread as it rolls through the contact patch. If as it appears to be, it's like all the rest of those that I've ever seen (save for one other private app), and it doesn't.

Typically this difference falls in the 3%-ish range (you might find a tire that's within 2% and I know you'll find others out around 3.5%), which doesn't mean much of anything for street driving evaluations. But it very well might at autocross where 2 mph less at 60-ish would more frequently put you in 'dammit, I have to upshift' and 'do I have to upshift or can I let it rattle along on the rev-limiter' situations.

I don't fault that app's developer beyond a simple lack of awareness as to how tires actually behave.


Norm

 

[MrMagnetic]

Is there a preferred brand or source for 5mm hubcentric spacers? CJ Pony Parts has 1/4" spacers but that may be slightly too big.

Is the camber mod documented aside from the Helm manual? Having a manual is always a good idea but $177 is :shocked:. I haven't yet found the mod in a search.

 

[NightmareMoon]

I can find the link to the slotted strut mod, but IDK somebody was saying at the factory procedure was changed to use camber bolts, so I can't rightly advise which way you're supposed to do it now to best stay within the F-Street rules.

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