Lotus Elan

Tire Report

PostPost by: TonyC » Mon Jul 19, 2004 4:03 pm

<!--QuoteBegin-type26owner+Jul 19 2004, 03:25 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (type26owner @ Jul 19 2004, 03:25 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> Love to debate these issues with you guys. This is the fun part of this forum. Tony, my apologies, it was Tune To Win I was refering to earlier. You do understand why I'm super cautious about taking advice from persons I don't know.....the input is welcomed though. For me this is where the real fun of Lotus ownership and operation is achieved. :D

[/quote]
oh I do indeed know, Keith. Sad as it is, I've spent many years chatting to folk on car forums and some of the stuff that appears can be startling. Bizarely people always want to believe the guy talking nonesense and not the guy talking sense! (Not in reference to anyone here - he quickly adds! :) )

It's certainly prompted some brain thought here, and having thought (and been told) more about the tyres I can underestand why they might be used. Never thought of that one - neat trick for cheap wet weather race tyres!

I think I'll need a cup of tea and a further ponder on these questions.
My own race car setup if much easier as the MG has a heavy old live axle flapping around at the back so I'm limited in what I can adjust.
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PostPost by: type26owner » Wed Jul 21, 2004 12:23 am

Tony& Rohan
Got the tire pressures sorted and the handling was okay when the left rear = 68psi, right rear = 64psi and both fronts = 46psi. I gotta get some wider wheels by at least another inch. Running these kind of pressures is nerve racking. Time for a beer. I walked the pits and I was the only fool out there running All Season Passenger tires. Still all in all it was a blast. I don't think I was the slowest one out there....
Let's see, only lost the hairpin throttle return spring once. Oh and my day ended when at the end of the fourth half-hour session I tore the left side engine in two. Somehow I knew that mount was going to fail since I tried to order new ones and only that mount was and still is backordered. The alternator laided down on the steering shaft and it made the steering wheel buzz in my hands. Drove for the two hour trip home though okay and when you can do that with a Lotus it's a damn good day. :D :D :D
Thanks guys!
-Keith
p.s. Rohan, those extra bump stops on the struts were the trick setup. Got some photos of me going through turn three (really off-camber 120 degree right-hander taken about 60 mph) with both inside tires just barely touching the pavement.
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PostPost by: rgh0 » Wed Jul 21, 2004 3:47 am

Keith
It sounds like you had a lot of fun. Post the photos if you can, as looking at the attitude the car is taking in the corners may help diagnose further how to get more out of the handling with more normal tyre pressures.

If you still have the original steel wheels replace them with wider ones soon or get them crack tested often as they will rapidly fail given the use you are making of the car on the track. Rear stub axles probably also need replacement or regular crack testing also if they are still original. These original components dont stand up well to the high cornering loads you describe and make a mess if they fail mid corner.

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PostPost by: steveww » Wed Jul 21, 2004 9:26 am

I noticed a significant improvement when I fitted 5x13 wheels (minilite) with the 155 tyres to my S4. That extra 0.5" makes a lot of difference - size matters :D

The steel wheels on my S4 were the original ones with the inner rivited to the outer. These are known to fail as well as being heavier than minilites. Much happier now that I have some confidence that the wheels are not going to fall off :unsure:
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PostPost by: type26owner » Thu Jul 22, 2004 3:08 am

<a href='http://briefcase.yahoo.com/[email protected]' target='_blank'>Thunderhill Trackday Photos</a>

Rohan,
This is picture is actually taken at Turn 14, I think. Still was tuning the pressures so this is not at full speed. You can kinda make out the rear tire pooched out in the shadow. Never did figure out the best line to take through there! Shrunken photo does not show the front tire lifted so I left it a big file. Big enough so hopefully you've got a fast internet connection.
-Keith
<a href='http://www.thunderhill.com/map.html' target='_blank'>Thunderhill Map</a>
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PostPost by: rgh0 » Thu Jul 22, 2004 4:09 am

Keith

Great photo, I do wonder were the apex is though!

A few comments based on looking at lots of Elans in similar photos

The tyres are not lacking for grip you are getting up a good amount of roll assuming the car was stable in the corner when the shot was taken. They do look to wide for the rims and are rolling a little

The rear bump stop spacer is doing what it is intended to do and stops the rear squat you get on roll and is helping control the roll itself.

The nose is down a little with all the weight on the front left. Unless you were still braking hard in the photo, stiffer front springs would help I think. If you can get hold of some old plus 2 sagged front springs try these. These help on the track and are fine for normal road use or get the equivalent made new.

Overall ride height appears to be a little high. The rear can jack itself if the ride height is to high and the A frame is angled down when side load imposed. This is one of the reasons for some of the funny turn in handling of an Elan especially under heavy braking. This jacking does not happen if ride height is low enough or body roll fast enough so that the A frame is level or pointing up when side cornering loads applied. If you drop the ride height a little you may need to reduce the bump stops spacers in proportion.

Rear camber looks a bit too positive, even given the amount of body roll. This may just be the inner bushing distortion and the angle of the photo but I would check the static camber and think about poly bushes at the rear. If you really want to do some work consider putting a little more static negative camber via adjusting the top strut mount or making an adjustable A frame.

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PostPost by: type26owner » Thu Jul 22, 2004 5:03 am

Rohan,
Great photo, I do wonder were the apex is though!

The left side tires are actually halfway up on the blue and white brem at the turn10 apex.
The tyres are not lacking for grip you are getting up a good amount of roll assuming the car was stable in the corner when the shot was taken. They do look to wide for the rims and are rolling a little

At about 30psi those rear tires would have been peeled right off the wheels, trust me.

I had a similiar opinion about the ride height. The front and rear ride heights are at the stock values. If I lowered the rear about an inch it would roll onto the bump stop sooner and maybe put the inside lifted front tire back down on the pavement. Can I cheat and put extra bump stops on the front dampers too? I don't want to throw anymore money at it except for fixing the safety issues. Upgrading the wheels and tires are definitely safety items.

The HTR T4s performed okay but the pressures needed to dampen the springback was excessive. They showed even wear and no feathering. They even picked up rubber on the inside edges of the outer tread blocks. Could barely build any heat in the tires. Never got them more then about 15C above the ambient. Ambient had to be close to 40C (100F).

.....think about poly bushes at the rear.

I designed a much better nylon bushing solution which does not bind up the suspension for the 41. A properly designed bushing needs no lubrication and when a detached a-arm is pivoted up on the bushings and let go it falls all the way down due to it's own light weight with an LC1 fit. Poly bushing totally suck compared to these. If I makeup a set nylon ones for my car would you like to try a set too? They're about an hour's effort so it's no big deal. That will make us even then. :)

I don't think it was jacking. It's been thirty-five years ago when I owned a VW bug which did.
Thanks,
-Keith
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PostPost by: rgh0 » Thu Jul 22, 2004 6:35 am

"Can I cheat and put extra bump stops on the front dampers too?"

Bump stops of the type described in the Carrol Smith books would certainly help at the front in place of stiffer springs if you can find some of the right spring rate that will fit the rather small space available.


"If I makeup a set nylon ones for my car would you like to try a set too?"

I guess I was using "Poly Bushes" as a generic term for any plastic / polyurethane bush that stiffer than the orginal rubber. I use a machined hard plastic ( nylon or HDPE not sure what) bush with the type of fit you describe from the Elan Factory both fornt and rear. The A frame and front arms when disconnected drop under their own weight.


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PostPost by: jrwiseman » Thu Jul 22, 2004 4:33 pm

<!--QuoteBegin-type26owner+Jul 22 2004, 03:08 AM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (type26owner @ Jul 22 2004, 03:08 AM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> <a href='http://briefcase.yahoo.com/[email protected]' target='_blank'>Thunderhill Trackday Photos</a>

Rohan,
This is picture is actually taken at Turn 14, I think. Still was tuning the pressures so this is not at full speed. You can kinda make out the rear tire pooched out in the shadow. Never did figure out the best line to take through there! Shrunken photo does not show the front tire lifted so I left it a big file. Big enough so hopefully you've got a fast internet connection.
-Keith
<a href='http://www.thunderhill.com/map.html' target='_blank'>Thunderhill Map</a> [/quote]
Keith

Looks like fun !

Are you using the original Lotus steering wheel ? Its little hard
to tell from the pictures.

good luck
John
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PostPost by: paros » Thu Jul 22, 2004 6:41 pm

Tyre pressures on my Elan S4 used for historic racing with either A032R tyres on 5.5 Minilites or more recently ACB10 in A24 [ ambient around 30 to 40 C ] and 14 or 15 psi cold- gets to 20 hot. The tyre temperatures around 80 C after a cooling down lap. plus lots of negative for Yokohama and only 1.5 degressfor ACB's. Car slides a lot and lifts inside wheel at front as it should do - and wins!!!!!
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PostPost by: type26owner » Thu Jul 22, 2004 8:13 pm

John,
Yep, it's the original wooden steering wheel. Only reason I haven't changed it for safety reasons is with the new Schroth 4-point harness and the fact I've got the seat all the back there's little chance now of my chest getting impaled on it. The harness system I designed and built took as much effort as the rollhoop did to do timewise. I'm still walking around with a dumb grin. :D

Paros,
I especially like the drifting too. Got the hang of it right away, when it was time to change directions a throttle lift or a brake stab was all it took to plant the fronts, steer it in and then right back on the happy pedal.

If I put anymore grippier tires on it then all my suspension settings are going to be too soft. My car spends about 99.9% commuting and only 0.1% on the track.
Regards,
-Keith
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PostPost by: jrwiseman » Thu Jul 22, 2004 8:29 pm

<!--QuoteBegin-type26owner+Jul 22 2004, 08:13 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (type26owner @ Jul 22 2004, 08:13 PM)</td></tr><tr><td id='QUOTE'><!--QuoteEBegin--> John,
Yep, it's the original wooden steering wheel. Only reason I haven't changed it for safety reasons is with the new Schroth 4-point harness and the fact I've got the seat all the back there's little chance now of my chest getting impaled on it. The harness system I designed and built took as much effort as the rollhoop did to do timewise. I'm still walking around with a dumb grin. :D

Paros,
I especially like the drifting too. Got the hang of it right away, when it was time to change directions a throttle lift or a brake stab was all it took to plant the fronts, steer it in and then right back on the happy pedal.

If I put anymore grippier tires on it then all my suspension settings are going to be too soft. My car spends about 99.9% commuting and only 0.1% on the track.
Regards,
-Keith [/quote]
Keith

Have you posted comments and/or pictures on your rollhoop stuff ?
It looks pretty nice from the pictures and I would be interested in
any details you have to share.

You might also consider an aftermarket steering wheel for racing, the originals
are pretty weak. Mine was an early casuality :( Later [ of course ] others
pointed out this weakness :)

have fun [ as you are apparently doing ! ]
john
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PostPost by: type26owner » Fri Jul 23, 2004 3:08 pm

John,
Have you posted comments and/or pictures on your rollhoop stuff ?

Yes, I've mentioned about sharing the design before but there was no interest. My design differs from all the others in two important ways. One, it does not secure to the any of the seatbelt attachment points so they are not ripped loose in an event. Two, the main hoop tubing is oversized to make it strong enough so the normal diagonal bracing to the top could be eliminated. Did this so the hood (softtop) could be modified to fit through the rollhoop minus the forward brace. Designed it to meet the current SCCA specs. That's why it's a couple of inches ABOVE my helmet.

Got two items which are not documented though. The angled steel bracket I added to the chassis inside the flared out section leading to the rear strut towers. The other is the doubler bracket which grips the chassis in the passenger footbox for the forward pointing removable brace. Photos are best I can do there. Everything else was done as a 3D model with detailed drawings. I'll gather up the info and make a new folder in my briefcase and point a link to it in few days.

Would replace the orginal steering wheel for trackdays if I had a quick-release hub system which would engage both wheels. That's probably the best theft prevention solution going. It's on my future to-do list.
Regards,
-Keith
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PostPost by: jrwiseman » Mon Jul 26, 2004 2:48 pm

Hi Keith

Any details on the rollbar design would be appreciated.

thanks
John
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PostPost by: type26owner » Tue Jul 27, 2004 1:37 pm

John,
It'll take awhile longer then I thought to retrieve the rollhoop info if at all. Had the final 3D model on my dad's computer since I did the fabrication over at his place. Emailed myself the file last Sunday and found it is corrupted and won't open. On top of that his computer has blue screened right after sending the email and now it won't boot up at all. :(

This is not the real sad story though. I've got a model of the 41 in which I've invested several hundred hours effort so far for which I may have lost the final version. Time to finish that project I guess. :blink:
-Keith
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