Leaf spring problem

trikesrule · 23 Mar 2007, 21:16 (Ref:1874776)

Guys the Speedway team I'm with have purchased a 'Junior' car. It's a 80 Corolla with a 3k engine. I was laying under the car checking things out (some of the crap you see is amazing) and making notes of of possible areas to be immediately improved. So going to the back first (the car was up with blocks under the tyres and the shed floor is dead flat). The right rear leaf spring is virtually straight and the left rear leaf is bending the wrong way. Before we purchased this car I have watched this car spin spin spin and thought something amiss there and mused about it. Well the laughter is on the other foot now cause I have too fix her. Now the Rule Makers said NO to me cutting the floor and raising the hangers so I can have the springs reset and regain some suspension movement and they said NO to when I suggested lowering blocks. My intention was to retain the running heights it's set too as it's not far away. Everything must remain visually standard thats the bottom line. Sooo has anyone any fabulous suggestions or should I just reset the leaf springs and raise the rear put the car on the scales and possible raise the front as well.............trikes

graham bahr · 24 Mar 2007, 15:54 (Ref:1875088)

sounds like you need to have the springs re tempered and decambered whilst at it, that will give them both the correct shape and the ride height you desire

bdwoody · 24 Mar 2007, 21:26 (Ref:1875242)

If the car is being used on an oval track we used to use new single leaf springs and have the ends hydraulic pressed to lower the car to the ride hight required..one higher than the other..

coln72 · 26 Mar 2007, 01:00 (Ref:1876336)

Yes, you need to get the main leaves reset. They should be able to be reset to what ever ride height you wish if the rules allow.

I also run a Corolla, but racing on dirt circuits, and found that I had to soften the rear leaves by removing a leaf fom the pack to try and reduce the amount of oversteer I was experienceing.

Also check to make sure you dont have a dud shock under there aswell and while your under there unbolt the rear antiroll bar as it will cause excessive oversteer on dirt.

trikesrule · 27 Mar 2007, 10:29 (Ref:1877504)

Took the shocks out and checked them out and all ok. Recorded their numbers and put them back in. Our car model isn't allowed to run a rear sway bar. If it did it would be ditched. I can't run a single leaf cause it's not standard. But I reckon I could get away with changing the number of leafs (rate). A re-set is planned for next week. The right front strut is very cleverly bent about half way down to give the right front wheel some camber. Who ever did that did a really good job.........trikes

coln72 · 28 Mar 2007, 01:52 (Ref:1878127)

Mine has had the front crossmember redrilled to move the pivot point out about an inch (and up slightly). Dont think there is enough metal to do this on a later model though.

Technically this is illegal but no one has noticed as the crossmember is covered with mud

trikesrule · 29 Mar 2007, 09:36 (Ref:1879019)

Hey coln72 we have to leave our suspension pick points std also. That totally sucks as the kids that drive these cars are not driving a car that is resistant to roll overs. R/o' happen regularly in this class. So it will be a challenge to get this car to 'sit right' on the track at speed. We're not even allowed to put specialized shocks like Afco or other speedway shocks in. This scenerio is just plain dangerous to me. I'm glad one of my kids dosen't run this class. The cars really are a bad accident looking for a place to happen. But I'm making noises so the powers that be can have a look at fixing some of the stupid rulings...........trikes

coln72 · 30 Mar 2007, 02:34 (Ref:1879618)

Trikes - even though you are stuck with the standard shocks, you could refill them with a thicker oil to try to reduce some of the body roll. Just dont use old sump oil like I did the first time, the seals didn't like that too much........

trikesrule · 30 Mar 2007, 22:30 (Ref:1880166)

Old sump oil? Coln72 did that help with your traction problem? I smell a new thread.........trikes

coln72 · 31 Mar 2007, 05:36 (Ref:1880271)

Stiffened the front up nicely until the oil ate the strut seals and pumped itself back out

If you dismantle the front strut, empty the original oil out and refill with the correct amount of hydrolic oil it should be good. I have the correct amount of oil in a manual somewhere around here.

Bikes have been doing this since the word go. I no of an Anglia that had grease nipples fitted to its front struts...............

trikesrule · 31 Mar 2007, 22:52 (Ref:1880754)

Hi Graham. What do u mean by decambered?.......trikes

trikesrule · 31 Mar 2007, 22:56 (Ref:1880756)

Coln72 I will have a good hard think and do some research. But I reckon mucking about with shock oil viscosity might be the way to go......trikes (grease hhmm)

trikesrule · 31 Mar 2007, 23:00 (Ref:1880759)

bdwoody I asked the powers that be about single leaf springs. He yelled NO!!! then chuckled and said it must be visually std. Said I'd get away with removing maybe one leaf (grey areas - I found another).........trikes

coln72 · 1 Apr 2007, 23:38 (Ref:1881628)

Shortening a leaf isn't exactly removing them...........its still there

johnny yuma · 4 Apr 2007, 05:18 (Ref:1883075)

Don't shorten the secondary springs forward of the axle,clamp them to the main leaf to avoid axle tramp,shorten them progressively behind the axle to soften the rate.

trikesrule · 4 Apr 2007, 11:04 (Ref:1883280)

Yep I'm listening guys...........trikes

coln72 · 5 Apr 2007, 03:19 (Ref:1883777)

get hold of a copy of Carrol Smiths "tune to win" as it has a chapter on sedan racing and a small section on leaf springs.

I've never had a problem with tramp by removing the bottom leaf.

johnny yuma · 5 Apr 2007, 06:36 (Ref:1883819)

If you have 4 or 5 leaves in a spring you could certainly take out the bottom[shortest] one and not have a problem.Tramp in a leaf setup is windup,if you have the front half of the spring which is under the main spring as long as possible,and clamp it to the main spring with a small U-Bolt close to the eye,the combined thickness of the two makes it difficult for tramp to occur .When a leaf spring is built mainly to carry a load and have a smooth ride,if driven aggressively the axle housing tries to ride up the spring,then flicks back,then tries to ride forward again etc. Circuit cars have different priorities.If the back half of the leaf setup is too flexible tramp under brakes can result,but usually springs are reset flatter to lower the car and this helps all areas.Lowering blocks cause tramp as they give the banjo more leverage on the leaf to twist it.

coln72 · 5 Apr 2007, 07:25 (Ref:1883855)

Just stuck my head under the bum of my car and the springs consist of two leaves.

I'm not disagreeing with you Johnny. Just this setup, being used in a motorkhana vehicle doesnt cause me any probs. Actually used to tramp before the springs were modded

trikesrule · 5 Apr 2007, 21:45 (Ref:1884472)

Yep jy and coln I hear u. First I need to see (this weekend) the car on the track before I go changing rates then implimenting the brains trust suggestions I will begin to play. Anyone know where I can get a Leaf Spring Rate Checker. I could make one if I had that elusive thing called time. But I haven't so I'll have to bite the bullet and purchase one. Anyone got one laying around they want to off load?.........trikes

Dennis.Doyle · 10 Apr 2007, 06:55 (Ref:1887701)

Quote:

Originally Posted by trikesrule

Yep jy and coln I hear u. First I need to see (this weekend) the car on the track before I go changing rates then implimenting the brains trust suggestions I will begin to play. Anyone know where I can get a Leaf Spring Rate Checker. I could make one if I had that elusive thing called time. But I haven't so I'll have to bite the bullet and purchase one. Anyone got one laying around they want to off load?.........trikes

Another trick I've seen to lower a car using standard leaf springs is invert the second longest leaf & shackle it to the longest. This effectively straightens the combined spring hence lowering the car. Two things to watch out for though. First I reckon it softens the spring rate as one of the leaves is now trying to regain it's original shape rather than being deflected from it as it is compressed. Second, it could lead to a fatigue failure where the ends of the second longest leaf meet the longest leaf. That said, it seemed to work quite effectively on a Lancia Fulvia I competed against.

Re. measuring the rates, you don;t need to make anything, simply stand on the spring whilst ensuring the ends can slide along the ground as it spreads. Your weight in pounds divided by the deflection in inches == the spring rate in pounds per inch. It's easy enough to get an accuracy of at least 90% which is good enough for most of us.

trikesrule · 10 Apr 2007, 08:38 (Ref:1887760)

Dennis thats real clever. Never even entered my head to check the rates that way. Certainly would give me a quick guide on which way to go.........trikes

trikesrule · 10 Apr 2007, 08:42 (Ref:1887763)

Lent my copy of 'Tune To Win' and never saw it again. mmm not impressed......trikes

coln72 · 11 Apr 2007, 12:32 (Ref:1888978)

Kick my ass later and I'll scan it for you

trikesrule · 14 Apr 2007, 04:17 (Ref:1890834)

No you'd better not coln (or it might be your ass). I've had a Leaf Spring reset some 70mm higher. The LR is some 40mm higher (static) than it was. Yet to get the car on scales. My aim is to get that RR digging into the dirt and get some diagonal weight transfer happening. This will make the car hook up a lot harder exiting (dirt oval) on the RR. Seems to be the way to get it all happening on the clay. I'm setting this rolla up like our title winning Bomber. And they didn't catch that. Let the games (development) begin........trikes

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