Soft RR

[dfhotlm33c]

I have noticed that many 4-bar e-mod racers tend to run a very soft RR spring. One that I wrench for runs a 95 RR spring on his 4 bar mod. I know it's not apples to apples, and there are a ton of other factors, but he was suggesting I attempt a softer RR than my current 225. I explained that 200-225 is standard for most LMs, and I was wondering why mod guys tend to focus on that corner more...

[MasterSbilt_Racer]

I have noticed that many 4-bar e-mod racers tend to run a very soft RR spring. One that I wrench for runs a 95 RR spring on his 4 bar mod. I know it's not apples to apples, and there are a ton of other factors, but he was suggesting I attempt a softer RR than my current 225. I explained that 200-225 is standard for most LMs, and I was wondering why mod guys tend to focus on that corner more...

Maybe it works because they have trouble generating body roll because the skinny tires make little lateral grip when it is slick? Maybe it is just because they tend to be behind late models on the technology curve? You don't see all the mods with the rf down attitude. They may still be drag racing. (Trying to make corner exit tight and maximize corner exit handling.)

[manwplan]

There's a lot of smart guys that race modifieds. There's a lot of smart guys that race both mods and LM. You would think that some have tried to run similar things on a mod that you would on a LM to get a nose down attitude. A lot of smart shock guys also involved with both. There has to be a reason why no one does. I'm going with the skinny tires and poor geometry of a stock clip.

[Kromulous]

I think a LM tire, on the RR with about 10lbs of air in it is alot softer (compressing, and bigger volume of air) than a Mod tire. Be it side wall stiffness etc.

I wonder if you can measure that, a tire squisher dyno? LOL

[Lizardracing]

I think that's a lrge part of it right there. On my car I can get 60lbs of bite change just with two pounds of air pressure on the RR and RF and about 30lbs change swapping springs. That makes the tires a act like a bigger spring than the actaul spring.
A stock clip has limited adjustablability and not as much aerodynamics as a late Model to make nose down/a55 up attitude worth more speed.
They are also narrower by ALOT so the suspension angle change is quite different between the two. Modifies are so naturally tight because the back end works so much better than the front end they get very sensitive so its common to use setups that favor the RR to get them free enough to turn on the throttle. Kind of like a sprint car relies on the RR to turn because the wobbly front ends don't offer a lot of help.

[billetbirdcage]

There's a lot of smart guys that race modifieds. There's a lot of smart guys that race both mods and LM. You would think that some have tried to run similar things on a mod that you would on a LM to get a nose down attitude. A lot of smart shock guys also involved with both. There has to be a reason why no one does. I'm going with the skinny tires and poor geometry of a stock clip.

Watch the top 5 or so USMTS cars, Like Gustin, Dillard, VanderBeek, Hughes, and etc. They are looking more like the LM attitude every week. Granted those cars are a little more open on what you can do to them then some of the other modified classes.

I'm not sure there is as much aero advantage in the mod doing so like the LM due to the body differences, but how knows for sure.

[powerslide]

We tried it and kind of came to the conclusion the aero wasn't there to help it like a late model. Granted we run a small stop and go track mainly so it may of been the track too. If you watch the USMTS and bigger IMCA shows those guys are layed over on the RF and all cambered up, but IMCA cant run bump stops. Seems like the IMCA guys have trouble taking off but once they get wound up it doesn't seem like they have the same forward drive issues, most of those guys are on the crate motor.

[powerslide]

Watch the top 5 or so USMTS cars, Like Gustin, Dillard, VanderBeek, Hughes, and etc. They are looking more like the LM attitude every week. Granted those cars are a little more open on what you can do to them then some of the other modified classes.

I'm not sure there is as much aero advantage in the mod doing so like the LM due to the body differences, but how knows for sure.

Billet Treed me

[billetbirdcage]

I think a LM tire, on the RR with about 10lbs of air in it is alot softer (compressing, and bigger volume of air) than a Mod tire. Be it side wall stiffness etc.

I wonder if you can measure that, a tire squisher dyno? LOL

There are plenty of spring rate checkers out there for tires. For example: A WRS-2 Spec LM tire changes roughly 32# of spring rate per pound of air (or least used to as I haven't checked one in years). Different constructions of tires carcass's have different rates and are effected differently with air.

Never mind the variance they have in them from the factory, that is a whole other story.