Imca Sportmod Rear Percent

[dereksehi]

I'm running a leaf sprung northern sportmod with 54% rear w/o driver and can't get any forward drive what kind of rear percent is everybody else running with these cars.

[stock car driver]

nobody is running a leaf spring car

have you got brand new springs in it? when I ran a nova if it lost drive it needed new springs, about every 3 nights for the left rear.

[dereksehi]

Springs are new only 2 nights on them

[stock car driver]

I would convert it to a 3 link if it were me. Its not much work.

[dereksehi]

What would be the benefits of the three link other than adjustability would it have more forward drive I have never run one?

[stock car driver]

leaf springs lose rate from the time they are put on

[72Dubya]

3 link offers better adaptability for changing track conditions. Not a lot you can do at the track with a leaf spring car to adjust for a changing track. Also, maintenance is A LOT easier.

A lot of guys also talk about a three link having improved forward and side bite over their old leaf spring setups.

[racin6mod]

send a pm to scooter m40 he's the guy behind the fast boys set up and was maybe the best ever with leaf springs.you wont be able to run the fast boys set up but he knows leaf cars.

[autoshop]

can you move the front of the springs up any holes, we use to run 56-57 percent rear. shocks staggered. lf in front

[dereksehi]

I can't move any holes up there is no adjustment I have the lr ahead and rr shock behind I went up to 56.5 percent rear and might take a little gear out.

[dirtrace09]

58% rear. If the right rear is clamped up and not floated move the shock back to the front (on multileafs). Take the spring pack apart and rearch the front of the left spring to 8 inches and right to 7 inches. Keep the band off the back of the left rear. Run 93 or 94 shocks on the back.

[dereksehi]

If I go up to 58% rear I would be about 150 lbs over the minimum weight or is rear percent more important than overall weight?

[dirtrace09]

Leaf cars typically need rear percentage to get forward drive. I do agree though that a 3 link car doesn't take the upkeep that leafs take.

[DaveBauerSS6]

leaf springs lose rate from the time they are put on

Leaf springs lose arch from the time they are put in. Rate stays the same.
Loss of arch decreases thrust angle, thus a loss of forward bite.

[DaveBauerSS6]

nobody is running a leaf spring car


Building one as we speak. Inspired by the success of the Skylark ; We'll see how it runs.

[DaveBauerSS6]

If I go up to 58% rear I would be about 150 lbs over the minimum weight or is rear percent more important than overall weight?

If you think you have enough motor to carry it and the weight is in between the axles, Ya.

[stock car driver]

Leaf springs lose arch from the time they are put in. Rate stays the same.
Loss of arch decreases thrust angle, thus a loss of forward bite.

Sorry, when I raced a nova I built a rater and used scales to test them..

the final straw for me was when my lr lost 70lbs of rate in one night on a heavy track

[dirtrace09]

Can you run composite leaf springs in IMCA? I am not sure of the rules. If so, run them with a panhard bar and they work great. I ran them on a ump modified before.

[DaveBauerSS6]

No composites allowed in IMCA.

[Krooser]

Leafs still seem to work fine on heavy or rough tracks. I'd build a bracket to hold up the rear frame of your race car while hauling it to the track… and keep the weight off of the springs until you are ready to race.

I ran with a lot of leaf cars in the past that would beat down most any three link… I have a leaf super stock right now that will be next winters project car.

[dereksehi]

Has anybody ever tried a half leaf rear suspension. Kinda like a 3 link but use the front part of the leaf as the lower trailing arms and cutting the rear half off and using a coil spring on top of the rearend on each side. Then putting the solid pullbar on top of the rearend with a panhard bar behind the rear. I believe it would pass tech as long as all of the rearend links are within the specified length. How well would a setup like this work?

[stock car driver]

rules are on imca.com

you can only have one spring per corner

[dereksehi]

It would only be one spring per corner since the leaf wouldn't go all the way to the back it wont support any weight it would function as a trailing arm not a springing mechanism.

[stock car driver]

No it wouldn't that would still count as a spring, lol.

[dereksehi]

If it would be considered a spring what would its rate be since its a flat piece of steel if there isn't any rate then its not a spring

[stock car driver]

If it would be considered a spring what would its rate be since its a flat piece of steel if there isn't any rate then its not a spring

Rules are rules a spring cut in half is still a spring.

Im not going to argue Ive done nothing but try and help you which seems to be futile.

good luck

[modified9]

Rules are rules a spring cut in half is still a spring.

Im not going to argue Ive done nothing but try and help you which seems to be futile.

good luck

back in late 80s early 90s there were several cars that had half leaf with a coil how do u run a monoleaf car 2leafs 2 coil springs