Lotus Elan

Tire Brand And Size?

PostPost by: rgh0 » Wed May 18, 2005 11:53 am

Robb

On my Elan one of the front shock tops comes though the fibreglass by about 6mm the other is just below the glass. Assuming the shock rubbers are in good condition and the front towers not bent then what you are seeing is just normal variation in the body moulding process. The holes in the body above the shocks were there for a reason and I assume it was so the shocks could come through if needed.

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PostPost by: type26owner » Wed May 18, 2005 2:09 pm

Robb,
The problem area of the Elan is limiting the roll on the rear suspension. Normally this requires adding a swaybar but there is a clever, simple workaround for that. Rohan turned me onto this trick. If you add another bumpstop which is 80mm long and really stiff under the stock one. Then by adjusting the ride height you can set your car up so it leans onto the bumpstop at maximum cornering bodyroll forces. This optimizes the weight distribution loading the tires so no corner is overloaded abruptly. One thing to remember is that when turning into the apex you can't just slam it sideways or a tire will be overloaded. The maneuver requires a smooth turn-in transition which is controlled by the driver. Being precise and smooth makes the car really, really stick. When it does reach the limit the steering goes completely light and playing the throttle keeps you on the bubble. The car should be very easy to recover if you get it out of shape.

The bumpstops I bought were really ugly florescent ones for an off-road vehicle to dress up the looks. The kind that never go off-road.
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PostPost by: type26owner » Wed May 18, 2005 3:00 pm

Hey Steve,
Here's an offer you can refuse. I'd be smarter just to buy you a set of RE92s to test against the XAS FFs since they are really dirt cheap. That way I don't end up with a really expensive set of tires I possibly don't like. Would you be willing to do this for me? I'm perfectly serious. Provide me your shipping address offline and I'll make sure you get a free set of tires out of this deal. I'll need an online discount tire vendor weblink over in the UK too. I'm not in big hurry though.

I've got probably about eight barely used or new tires in my garage already that handle like total junk. I'll haul them over to Mike Ostrov's whenever he has another seminar and give them away.
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PostPost by: steveww » Wed May 18, 2005 4:02 pm

Keith,

Thanks for the offer. I have looked through the usual online suspects for these tyres and no joy. I also checked Bridgestone's UK site and there is not any mention of the RE92, they only have the B330EVO which is only T rated. Looks like this is a USA only tyre :( Hmm just checked the Bridgestone USA site and again no mention of the RE92, the plot thickens.... However tirerack have them listed.

Interesting just searched tirerack for 155x13 and there are only 3 tyres to choose from and none of them look that great. You guys have it bad over there. You should move to the UK, the weather is cr*p but you can get classic car parts a lot easier ;)
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PostPost by: type26owner » Wed May 18, 2005 4:31 pm

Steve,
Try searching for Bridgestone Potenza RE92. Yup, the tire choices sucks here.
You should move to the UK,

What? Move to the center of the racing universe! I'm ready as soon as my wife and I retire. :D

It's raining here again in California today. You can take your weather back if you please. We've had enough for this year already. :rolleyes:
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PostPost by: robb4100 » Thu May 19, 2005 4:02 am

Keith,

The Front springs are adjustable and 2.5" ID and are extended about 7/8 of the total length (~ 3/8 in from end).

The rear springs are also adjustable and are about 1 inch from fully extended.

The sway bar is 5/8 in diameter.

I have so far been unable to determine the rating of the front springs. For what it is worth the spax shocks and front springs are the same color blue (about the same color as this page)

The rear springs are Bright red and I found a reciept for Eibach springs so I suspect that these are the same.

Does this help you?

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PostPost by: type26owner » Thu May 19, 2005 2:10 pm

Robb,
Unless you've got the spring rates listed on the paperwork then determining this must be done by comparing dimensions. We can compare the wire diameter and the number of coils between our springs to gauge what ones you've got installed. Mine are the Stage Two (halfway) ones from DBE. My DBE catalog which lists this stuff is over at my parent's house so it'll be later this weekend before I can look this info up. Pretty sure it will just list the springs by the rates and not give any dimensions so I'll get my calipers out and crawl under to car to measure on Saturday.

There's a good chance you've already got the trackday springs installed. The Spax are fine. Lot of folks claim the Koni's are better. Bet in blind test they couldn't tell one brand from another. :P The 5/8" swaybar is too weak and allows the car to roll so much the tire traction patch is impacted in a bad way. The outboard tire will roll up onto the outside shoulder and the inside shoulder will not be in contact with the pavement. Reading the wear pattern on the tire and measuring the temperature across the tread will make this perfectly clear the first time you come off the track after finding the diamater of the traction circle for the first time. So the intermediate front swaybar will cure this condition and make the tire stay in full contact with the pavement. I'll measure the diameter of the swaybar that I have installed because I don't trust my memory all that much anymore. Just add the bumpstops to the rear struts and set the ride height to the nominal value and you're ready to have some fun. With the setup I'm describing the car the car will be easy to drive at the limit. No nastiness.

One thing you might want to do while doing your suspension work is to bumpsteer the front suspension. Having it not dart around while going over the ripples makes the driving much more effortless. Do you need instructions on how this is done?
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PostPost by: type26owner » Thu May 19, 2005 3:22 pm

Rohan,
My main concern with these RE92s is the tire rotating on the wheels under heavy braking. I suspect they are moving slowly when they get really hot. Going to mark their orientation on the wheels this time and pay attention. Anyone add beadlocks to the steel wheels before? This was not a problem with the tires I had to inflate to 50+psi.

The KFP Magnum Blue carbon/kevlar brake pads I'm using are exceptional and are latest state-of-the-art ones. Lee at <a href='http://www.leechapmanracing.com/kfp_magnum_pads.htm' target='_blank'>leechapmanracing</a> recommended these pads but they are pricey at $200 for all four corners. The car will haul down from top speed without yawing violently about like it did before. In fact, I can probably take me hands off the steering wheel and it will pretty much track straight ahead so the amount of the rubber bushing deflection making it toe-out is not a problem. It squats the nose down solidly onto the bumpstops and there is no tire tramping. The pedal pressure is perfect with about I'm guessing 30-40 pounds required to lockup all four corners at any speed. This on the dead stock cast iron calipers and rotators. It's sweet now. No more suspension tweaking necessary.
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PostPost by: type26owner » Fri May 20, 2005 2:03 am

Hey Robb,
Suppose I should elaborate a little on the roll dynamics of the Chapman struts since they are quite heavy, unsprung weights and important to use in your handling favor. I've removed the resilient rubber donuts and have replaced them with double-ended cv joint halfshafts on the rear driveline. To partially make up for the loss of the roll centering restoring force the donuts provided similiar to what a rear swaybar would be providing the strut travel must be restrained to the same level as if the donuts were still there in jounce and rebound. This must be done in tandem to the roll characteristics to match how the front suspension reacts or the balance is compromised and a corner will be overloaded and that tire will break traction or lift up clear off the road. What I mean is along with a bumpstop to limit the jounce travel on the outbroad wheel while cornering on the inside wheel must not be allowed to rebound (droop) too much. Rohan uses a multi-stranded steel cable but I prefer to use a high-strenght nylon flat strap instead. I like the soft stretch of the nylon to eliminate the clunk noise a cable would make. The attachment point to the strut is below the adjustable spring perch so it can be moved up or down easily to contol the amount of rebound travel so I can keep the inside front wheel from lifting off the pavement. Be careful because the lotocone mounts are asymetrical in their engagement onto the chassis at the boltholes. In other words the same bracket won't work to mount the strap to the bolt on both lotocones.
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PostPost by: rgh0 » Fri May 20, 2005 10:02 am

Keith

Agree with your choice of brake pads I am using similar Carbon Kevlar pads and get similar performance. I run slotted/ spotted disks which give a little better response in the wet and on circuits where the brakes get very hot ( have you melted the rubbers on the steering track rod ball joints yet ?). Incidently what have you done to get the correct front rear balance ? I use old DS11 equivalent pads ( trade name "Blackflash" if they had that in the US) at the rear bu I am down to my last set and when these are gone I need to find a new rear pad or some other way to get the right balance

I have nylon front suspension bushes to limit deflection under brake loads but still find the need to increase the toe in to maintain stability under heavy and high speed braking. Maybe the Yoko A032R's I normally run are more sensitive to this compared to RE92's but I also find the same setting works with the Hoosier street TD's I also use.


The wire cable restraining straps dont cause a clunk. When they come into play the spring load is low but the shocker is still working at maximum effect so the velocity of the suspension is low and the cable takes up its tension without any significant clunk !

back to the garage now I have to get my new engine running tonight only 7 days to my next race meeting

Rohan
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PostPost by: type26owner » Fri May 20, 2005 12:58 pm

Rohan,
Okay, okay. Only mentioned the potential clunk to pull your cable a little. You're right of course. I couldn't resist putting a little burr under your saddle. All is forgiven?

Suspect the deflection of the front bushings to toe-out under braking is proportional to grip level of the tires. The RE92 have less grip than the racing ones. If this were not so I'd be lapping at the same lap time rather than 10 seconds slower. Since I've got about half the hp you do I'm also not needing to whoa the car down as much entering the turns. I drive the car with as little braking as possible similiar to the tactics a Formula Vee is forced to be use to be quick.

I'm using the KMP on all four corners and don't have a balance problem. That really surprised me. Figured I'd need a proportioning valve but that luckily is not required.

I have burned the rubber off on the tierods but not on the track. Was riding the brakes a tad too much while my brother towed me down a steep grade on a 6 foot long tether. That's also when I discovered why silicone brake fluid to no good when it gets hot. My brake pedal went all the way to the floor and did little to assist slowing the car.

Both my younger brother and I have given up on vintage racing for the most part. Trackdays are much less stressful and just as much or more fun. You certainly get lots more time out on the track for your money.
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PostPost by: type26owner » Fri May 20, 2005 4:04 pm

As far as I can tell the yellow dot on the RE92 sidewalls are suppose be to clocked on the wheel so the dot is just adjacent to the valve stem. I dimly remember them all being located there when the tires were freshly mounted. Now the dots are all over the place! Two are almost rotated exactly 180 degrees away from the valves stems. No wonder my balance has gone away. Worst case I can monitor the motion and swap the wheels from side to side to reverse the motion and keep the dot hovering around the valve stem. Bummer!

I've emailed Bridgestone engineering for advice.
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PostPost by: type26owner » Fri May 20, 2005 4:52 pm

The fellow at the TireRack advised me to roughen up the powdercoating on the wheel in the area of the bead to stop the tire from rotating on the wheel. He says they have to remove the corrosion all the time on the alloy wheels and they don't normally have the tire move as a result. Interesting. It's the simple solutions I really like if this will work.

BTW, he said the yellow dot is not required to clocked around to the valve stem anymore. The tolerances of the tires is held to such small errors now it's no longer necessary.

p.s. chicagojeff my apologies. Didn't mean to hijack your posting. Somewhere along the way I got confused and thought Robb was the guy that started this all.
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PostPost by: types26/36 » Fri May 20, 2005 7:54 pm

Hey Keith,
Just looking at your number of posts "666" hope you are not superstitious! :huh:
Brian.
Sorry..NLC
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