Lotus Elan

Avon acb 9

PostPost by: upnorthelan » Sat Sep 04, 2010 11:11 pm

I ran this season with Avon acb 9 (5.0/22.0 x13) mounted on stock (4.5") wheels and was left wanting more grip. I love the feel of bias plys and was curious if anyone's run the larger acb 9 (6.5/23 x13). I would mount these on 5.5" wheels. The main issue I'll face is fitting them under the car. I currently have stock fenders (S4) with inside lip shaved down pretty good. Sasco Motorsport quotes the 6.5" as being around a 170mm which I've read many people running, or larger, under stock fender. Anyone run these without flares?
Thanks,

Mike
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PostPost by: vintrace » Sun Sep 05, 2010 8:08 am

Hi Mike, I agree the ACB9 is a great tire. As you probably know it was really designed to run on a 5.5" rim so you are probably feeling them move around quite a lot.
The ACB9 6.5 tire is huge and I doubt very much if you could get it on the car. The problem is the 6.5 has a tread width of about 6.7" as the size would indicate.. however the side walls are very balloon like and the overall width of the tire is 8.5" this added to how tall the tire is would make it a very unlikely fit. The ACB9 does come in two compounds..the most common being the 25 compound.. they do a softer grippier one but to be honest when ever we have used it on a heavy ish car like the Elan we have smoked it in a couple of sessions. Have you used a tire temp gauge to see what your tires run at...? Well worth the investment if not.. those ACB9's like to be at least 160 deg to a max of about 190 deg.... over or under they get a bit greasy.
Another problem you may be having is running on a small rim you are pinching in the tire and 'crowning' it... in reality you may only be running 70% of the tire due to the shape you have made it on the small rim... again a tire temp gauge would give you temps across the tire and tell you just whats going on. Good Luck.
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PostPost by: upnorthelan » Sun Sep 05, 2010 7:07 pm

Thanks for the advise,
Maybe my next move should be to try a fresher set of the smaller acb 9s on a 5.5" wheel to eliminate crowning. Didn't think of how wide the mid section of the 6.5" would be. Thoese are a FF rear aren't they?
Mike
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PostPost by: cabc26b » Sun Sep 05, 2010 7:30 pm

Mike,

The size of 6.5x23 is a show stopper for you ( they are bigger on the car than on paper if that makes sense) . +1 advice from tony re compounds - . I also like the acb10's but some groups have an attitude about them - they have a 6x21 maybe you can squeeze that on/in but i think your running out of options with stock fenders as these too should be run on 5.5 or 6 inch rims. 6 inch rims are deal killer for stock fenders - I think if you play around with offset you can squeeze a 5.5 in there with the small springs etc.

George
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PostPost by: SJ Lambert » Sun Aug 02, 2020 4:41 am

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I’m thinking about using a set of ACB9s on my F2 Historic car as a set of wets.

I see that Avon put the A37 5.0/22 & 6.5/23 up as a pre 65 F3 option.

I’m on Avon 8.2/22 & 10.5/23 at the moment.

I’d have to make a new set of wheels to suit (can do it with proprietary centre castings and spun rims to suit).

The “ballooning” rears wouldn’t be a problem in an open wheeler.

My two questions are:-
1 - In my group, 10” wide rears lead to lots of aqua planing in the wet & earlier cars with FF style width tyres excel in the wet. Are these ACB9s a good wet tyre?

2 - I have long wheel studs in the rear hubs of my car & might have to muck around a bit to get a 6.5” wide wheel to mount without altering the hubs (which would defeat the purpose of having skinny wets to bolt straight on) - I see Avon say maximum width wheel to mount the 6.5/23 is 6.5” - As the section width is more like 8”, I wonder if it would mount on an 8” rim? I may have a discussion with Russel Stuckey about rim width, but I would be very interested in any opinions from readers here, even if they were to be cautionary !
Last edited by SJ Lambert on Thu Aug 06, 2020 7:43 am, edited 1 time in total.
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PostPost by: StressCraxx » Sun Aug 02, 2020 5:03 am

We use the ACB9 tires in vintage Formula Ford. We are allowed the choices of A29 (hard) or A25 (soft) compounds. I have run them in the rain at Thunderhill and Sonoma Raceways near San Francisco, CA and Road America in Elkhart Lake, Wisconsin over the last 5 years. They absolutely do not do well in standing water or streams flowing across the track. I have in car video to prove it. Wet or drying track they are fine, but suggest adding brake bias to the rear. Some drivers will change springs to softer rates, and disconnect their anti-roll bars. Sizes we use are 5.0/22.0-13M size in inches (7267A25) and 6.5/23.0-13M (7290 A25)

If it were allowed by our rules, I would run a more narrow tire in the rain to avoid aquaplaning and to increase the unit load upon the tire tread at each corner. YMMV
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PostPost by: SJ Lambert » Sun Aug 02, 2020 12:27 pm

Thanks StressCraxx!
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PostPost by: TWebb » Mon Aug 03, 2020 5:18 pm

New to the Elan as a racecar. So pardon the silly question.

Are Hoosiers not a good choice?
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