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running smaller tires for autocross?

 
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winddude  



Joined: 15 Jan 2020
Posts: 61
Location: Vancouver Island

PostPosted: Wed Jul 22, 2020 6:59 am    Post subject: running smaller tires for autocross? Reply with quote

I'm mostly going to be autocrossing with my car 1980 NA, I picked up a nice set of period correct ronal rims, with the correct bolt pattern and offset, they look great on the car. They seem to be similar in weight to the original 14" rims.

I'm looking at 2 sizes in the same tire:

1 - a 205/50r15, which is 4.5% smaller circumstance than the 185/70r14
2 - a 205/60r14, which is about 2% smaller circumference

Other than the speedo being out is there going to be much issue running #1? I was thinking I should have a bit better acceleration, and have read smaller diameter tires can improve handling because the tire is rotating quicker. The sidewall is about an inch shorter, so the ride might be a bit harder. Thoughts on running smaller tires?
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jacobroufa  



Joined: 18 Nov 2016
Posts: 293
Location: Rockford, IL

PostPosted: Wed Jul 22, 2020 12:05 pm    Post subject: Reply with quote

I went from a larger sidewall tire to 205/50r15 on my Weissach and I don't notice a difference in a negative way. I pick up a couple extra bumps, but the handling feels more sure-footed. The 924 is a pretty soft sprung car so until you go upping spring rates I don't know that it'll impact you in a harsh way.

Bonus on the 15" size is the spec Miatas run them so you have lots of tire choices.
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winddude  



Joined: 15 Jan 2020
Posts: 61
Location: Vancouver Island

PostPosted: Wed Jul 22, 2020 4:04 pm    Post subject: Reply with quote

thanks! That's enough info for me to hit the order button, lol

Next project will probably be higher spring rates and a thicker torsion bar.
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!tom  



Joined: 28 Aug 2006
Posts: 1907
Location: Victoria, BC Canada

PostPosted: Fri Jul 24, 2020 4:39 am    Post subject: Reply with quote

Where are you planning on autocrossing?
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winddude  



Joined: 15 Jan 2020
Posts: 61
Location: Vancouver Island

PostPosted: Fri Jul 24, 2020 5:11 am    Post subject: Reply with quote

western speedway. Wasn't enjoying the undeersteer on my caliber srt4 anymore, and tires would be about as much as I'll hopefully put into this car for the first bit. I've heard the Victoria Porsche club runs some events as well, but not sure if they are this year with covid.

Do you autocross, or do any of the track days? I see you're in vic as well.
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924RACR  



Joined: 29 Jul 2001
Posts: 8353
Location: Royal Oak, MI, USA

PostPosted: Fri Jul 24, 2020 8:37 am    Post subject: Reply with quote

We actually run 205/50/15's for road racing, works great - 'cause they're Spec Miata takeoffs. Keeps the costs down.

Have family in Vic... (but haven't been there in years)
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winddude  



Joined: 15 Jan 2020
Posts: 61
Location: Vancouver Island

PostPosted: Sat Jul 25, 2020 2:45 am    Post subject: Reply with quote

924RACR wrote:
We actually run 205/50/15's for road racing, works great - 'cause they're Spec Miata takeoffs. Keeps the costs down.

Have family in Vic... (but haven't been there in years)



Thanks, now I just need to find the tire, place I tried to order from now says they're out of stock.

It's nice here, but no road racing or climbs anymore. They built a nice new track on the island but apparently no racing or even timing.
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!tom  



Joined: 28 Aug 2006
Posts: 1907
Location: Victoria, BC Canada

PostPosted: Tue Jul 28, 2020 3:48 am    Post subject: Reply with quote

I've never done the autocross, but I know a few people who do at Western Speedway.

My car is currently sidelined, and one of these days I'll get around to fixing it. Might show up then, it looks like way too much fun.

I've been to VIR, it's awesome there. But, it's NOT a race track, as the land it was built on was re-zoned after it was built to preclude race tracks, with existing use provisions all revoked. So, if you call it that, they'll have to tear the facility down. It's a high performance driver training facility, and it's a darned good time too.

If you time your car there, that's racing, so it's expressly forbidden.
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