SREN set up info

Technical and Repair Discussions

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PostPosted: Thu Jan 04, 2018 12:39 am
I'm going to race a new to me Renault in a vintage series and at Waterford Hills (chassis # 246). Since hardly anyone is racing one anymore, would anybody be willing to part with their hard earned set up information? I have almost nothing but a log book and could use alignment, spring rates, shock valving (Koni), etc. Any information I can get will save me an awful lot of development time that I really don't have before driver's schools in the spring.
Brian Murphy

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PostPosted: Thu Jan 04, 2018 7:41 am
Find and talk to Charlie Greenhouse, if you contact me directly I will pass you his email. He has a stable full of SRENs.
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PostPosted: Thu Jan 04, 2018 6:25 pm
What tires do you plan to run? That will have a significant impact on the setup. If Hoosiers, I'd follow the Gen3 recommendations since the weight distribution of a Gen 3 is closer to the original SR in Renault trim. Downside is longevity, so, based on our experience at the 25 Hours of Thunderhill I'd recommend the Toyo R888R. We swapped rears mid-way, but they still had substantial tread depth; I believe we ran the fronts the entire 25 hours, plus a full test day.

If you have the original springs, they are much softer than the current springs used in the SRF (2/3), as we put the rear Renault shocks on the front and went with a new, stiffer rear spring (check the GCR for spring rate information.) You may find it desirable to stiffen up the chassis if you go with the Hoosiers as it will cut down the body roll. On the 25 Hour chassis, we went with a completed different shock/spring package (e.g. shocks adjustable in both rebound and compression), and substantially higher spring rates (running downforce front/rear, we needed to keep the chassis lower than the original springs / shocks would allow (BTW, if we ever decided to "upgrade" the shock/spring package, this would be a good and cheaper setup, and avoid some of the current issues with shock travel/bump stop bottoming).

I'm sure you'll get tons of Koni recommendations, but my recollection is that we ran 1/2 off full stiff in the back and 1 off full stiff in the front. Since they were a PIA to adjust (had to pull off car and remove springs/bump stop/plastic shield, compress the shock fully, then turn the shaft clockwise untill it won't rotate any further (now full stiff), then rotate the shoft CCW to desired point of adjustment), I didn't play much with the settings. May be worth a refresh/rebuild (which should be cheaper than the Penske's). My on-car shock check was to jump down on the back of the frame and see if there's noticeable compression damping (still my test of Penke's as well), and watch the time to rebound to see if it rises slowly (and no girgling or other noises indicated loss of fluid or loose bushings. My off-car "dyno" test was to hang the shocks with a small weight (2-5 lbs?) tied to the bottom, compress the shock fully, then time (in seconds) how long it takes to fullly uncompress (usually 5-10 seconds depending on the weights and stiffness setting.) This will give you at least a baseline to confirm there's still rebound damping in the shock and point out any major differences in damping across the shocks.

Alignment setting should be close to the Gen3 recommendations. Generally, a small amount of toe-out on the front (more for tight tracks/less for fast corners), then a slight amount of toe-in in the back. Bump is a pain to adjust, but it's a good idea to do at least a "string" test to determine if and how much each end of the car bumps in or out as you compress the suspension (good time to do this is when you have the shocks/springs out of the cars so you can easily move the suspension up/down from normal ride height). A little out is OK/desirable on the front. As close to zero as possible in the back (or a little in) is desirable. Suspension setup is a whole subject in itself so my recommendation is to just get it reasonably close until you've acclimated to the car, then fine-tune as need to achieve a reasonable balance between car handling and tire longevity.

There's a lot of useful information still available on the Mumm Brother's site so I'd suggest perusing that as well to get some ideas and recommendations:
Bob Breton - SRF 51 - San Francisco Region

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