Lotus Elan

where are you guys getting tires?

PostPost by: lotusdelta » Tue Jan 10, 2006 9:21 pm

hello everyone,
well its time to replace tires that where on my 72 elan sprint coupe when i first purchased it. it has dunolps sp400 i think,terific tires that really lasted ,
anyhow went to a couple places to inquire about possible replacements and got the blank stare....seems now a days nobody believes cars had 13 in tires ....can anyone suggest a good source stateside?
really wood like pirellis or dunlops...any help is appreciated

david
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PostPost by: gjz30075 » Tue Jan 10, 2006 10:37 pm

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PostPost by: type26owner » Wed Jan 11, 2006 3:26 am

David,
There are plenty of 80 series tires out there which are $40 All-Season worst tire you can buy econobox type. Just do a web search on P155/80R13. As long as you keep it below 80 mph they are fine even if you lean on them a bit. Above 80 mph and when doing what the car was intended to be used for those tires are not okay. The handling gets downright terrifying. You can improve them quite a lot but you'll have to pulp them way over the recommended air pressure to 50 psi or above. All of them are only speed rate as S or T and frankly not suited for high speed at all. They weigh 14 lbs typically because the sidewalls are paper thin and that's why they handle like crud.

Then in the middle is just one choice and it's the $50 Bridgestone RE92 P165/65R13. They will fit on the 4.5" wide wheels and clear the bodywork of the baby Elan. Only run these on the newer wheel with the safety bead if you're going on the racetrack. They have sidewall stiffeners which make the tire behave really well at any speed and stop the yawing back and forth on the brakes. 20psi is all they require. They are also H speed rated which gives one a bit of more comfort if you're taking it to the 120mph limit thereabouts. If you get the rears to heat up past 26 psi the car will tend to snap oversteer and I mean really quickly. You'll have the rearend hungout by 90 degrees in a flash. I'm just as quick while cornering as another Elan shod on Yokohama 032s which are race rubbers when they get hot ~150F. They suck on wet roads though. They weigh 19 lbs because of the stiffeners. The ride is not any rougher than econobox tires that I can tell. They don't have enough side bite on a fast road car to launch the car like a bicycle up on two wheels like the racing Elans will do either thank gawd. :D :D However on the stock springs it just might rollover because the bodyroll rate is such that the car wallows to the full suspension travel on both sides so be careful.

Then there's the top of the line racing donuts and I think only two choices here. The Michelin XASFF and the fore mentioned Yokohama 032.

Those are your only options here in the USA.
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PostPost by: lotusdelta » Wed Jan 11, 2006 1:45 pm

thanks everone for the feedback on tires....i contacted tire rack...very nice people and they have a pirelli p-400 tire in the correct size....also want to check out those bridgestones as i have bridgestone tires on another car and have very pleased..this is such great forum.....great people and great help......with the exception of how to jack up a elan.....that busts me up ...40 ways to do it..lol

thanks david
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PostPost by: type26owner » Wed Jan 11, 2006 5:07 pm

I'm disappointed again! No one is going to point out that putting 50+ psi in a tire rated for only 32 psi is dangerous? Any true believers that have drunk the Kool-Aid out there? There must be at least one just itching to say it. :lol:
p.s. Hey Ed, sorry you don't count. I know you're just yanking my chain. I'm on his offline list already. :P :shock:
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PostPost by: theelanman » Thu Jan 12, 2006 12:51 pm

surely the problem is the side wall and that inflating the tyre to just under exploding wont make the slightest difference to cornering......if it wobbles in a straight line then its not the tyre...it'll be either the tracking or the wheels......get em checked!!!!!
I run 26psi and the tyres I chose had a thicker side wall to reduce deflection....I wanted reinforced sidewalls but couldnt find them for my rims!!..
I agree that inflating your tyres way in excess of the manufacturers spec if dangerous......and if you get a blow out on a corner and smash your car up and then the insurance refuse to pay when they notice that your other 3 wheels were over 50psi dont say it wasnt mentioned.....
still dont understand what the reasoning behind too much air is....surely just makes the ride harder.....
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PostPost by: type26owner » Thu Jan 12, 2006 2:31 pm

Hi Theelanman,
Why the tire behaves this way when ulitized at the maximum I haven't a clue. It just does. The problem is easy to diagnose on the racetrack, just run the pressure up and down and the handling will change from stable to terrifying, back and forth. It ain't the suspension.

At first glance overinflating the tire seems dangerous but after looking into the engineering/physics it's actually not. The highest pressure is based on the highest load which for these tires it's rated 73H and that's 932 lbs and the highest rotational speed. The Elan front tires only get loaded about 600 lbs and the rears even less. There is loading capacity going to waste.

A tire is three hoops (1 tread, 2 beads) with two discs (sidewalls) connecting them. The first order approximation has the air pressure pushing out on the main hoop (tread) and puts the sidewalls into tension. When the tire is supporting the weight of the car the sidewall is in tensile load with the air pressure and at the same time that is canceled partially by a compressive load from the weight of the car so the sidewall bulges a bit. That's not what's holding up the car though. The wheel is actually hanging from the main hoop. That hanging force is tensile and when added to the tensile force of the air pressure that combined tensile force determines if the tire is within the safe operating envelope or not. Not intuitive at all, isn't it!

I don't know how much is too much pressure so my advice is don't do it. Just go buy a tire that will handle okay at high speed and not require you to put in over the recommended pressure to get the car to handle. You have no business pushing an 80 series tire past 80 mph. Been there, done that and will never do it again!

Next time you're tooling down the road just remember you're hanging in there! :P Sorry, I couldn't help it. I'll go wash my mouth out with soap now. :oops:
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PostPost by: theelanman » Thu Jan 12, 2006 3:10 pm

type26owner wrote:The first order approximation has the air pressure pushing out on the main hoop (tread) and puts the sidewalls into tension. When the tire is supporting the weight of the car the sidewall is in tensile load with the air pressure and at the same time that is canceled partially by a compressive load from the weight of the car so the sidewall bulges a bit. That's not what's holding up the car though. The wheel is actually hanging from the main hoop. That hanging force is tensile and when added to the tensile force of the air pressure that combined tensile force determines if the tire is within the safe operating envelope or not. Not intuitive at all, isn't it!
:P


whilst I agree with some of the above this doesnt not quantify the use of such pressures.....the material of a tyre by its own valition is in fact rubber...an inherently flexible material.....
this will therefore work in a similar way to an unbraced box relying totally on the rigidity of the material from which its made to provide its stiffness.....in structures we add crossbracing, wind bracing etc to brace and strengthen the structure to remove the deflection....
what you are doing on cornering is applying a internal force at the rim pushing out an external force at the tread pushing in the opposit direction which in turn is creating rotation about the sidewall and hoping that the weakest part of the tyre can cope!!!......
the hope is that the seal between the tyre band and the rim do not part....
rather you than me....I've just got propper wheels and tyres and theyre good to 110mph!!! no shake, judder, wobble, roll......its on rails!!!!

cheers
G
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PostPost by: type26owner » Thu Jan 12, 2006 3:50 pm

what you are doing on cornering is applying a internal force at the rim pushing out an external force at the tread pushing in the opposit direction which in turn is creating rotation about the sidewall and hoping that the weakest part of the tyre can cope!!!......

You lost me. Haven't a clue as to what your point is. Sorry.

Running the tires up to high speed is not the problem. The problem is when one applies the maximum loading a tire can undergo while threshold braking. Most folks have no clue as to what consititutes threshold braking. The pictures showing how it's done in Alain Prost's book are a real eye-opener. Once you see someone doing it properly you'll truely appreciate how hard it is and that they have a special gift. It's mainly what distinguishes the F1 drivers from us.
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PostPost by: type26owner » Thu Jan 12, 2006 5:14 pm

Are you referring to pneumatic trail?

My guess is when the threshold braking problem raises it's ugly head up the tire starts to tramp. You'll know because full rotations of the steering wheel back and forth very fast are required to keep the rearend behind you. It's a seat nipper moment if the tires really suck like the Michelin MX4 Rainforce did. Of course, the MX4 might be the worst ones to do this and your different brand does not. Hopefully that's the case.
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PostPost by: pamitchell » Thu Jan 12, 2006 5:52 pm

Any recommendations on 175-70-13 tires for S4?
Costco had Michelin X in this size but with v. hard treadwear index. 700+.
I'm planning on some autocrosses and track days this year but mostly using the car for weekend jaunts.
TIA
Phil Mitchell
San Jose CA. 69 S4/FHC
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PostPost by: type26owner » Thu Jan 12, 2006 8:26 pm

Hi Phil,
Yes, don't buy any tire which is speed rated for only S or T. H should be the very minimum. Thicker sidewalls are better. I think Falken might make a high performance tire that size which is H rated. Check it out.

Will we see you at Laguna Seca? It's a total gas to drive once you get over the intimidating hill a few times and survive. :D
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PostPost by: pamitchell » Thu Jan 12, 2006 10:32 pm

Thanks Keith;
Yes; I'll be at Laguna in Feb. I did the Audi Driving School there in 03 so I'm looking forward to revisiting the Corkscrew in the Elan.
The front suspension is being rebuilt this month so it will be a good time to sort it out.
Phil
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PostPost by: brandon » Mon Jan 16, 2006 6:46 pm

Can we actually get the Michelin XAS FF here in North America, or is this a Europe only tire? I have spent an exceptionally modest amount of time searching for these tires, and can't find them listed on any NA sites.
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PostPost by: type26owner » Mon Jan 16, 2006 7:11 pm

Coker Tire. Be forewarned they are jerks especially their tire engineer. He's downright dumb. Cost is about $200 each.

Boy did I get screwed by them. Can you tell I'm still pissed off?
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