tires hit fenders.

[Mojoluthier]

I have recently acquired a Westfield pre-lit, a very traditional 7, I'm told. In my search for a car I did prefer the clamshell fenders, and that's what I have. Unfortunately, they are interfering with the tires on the bumps, particularly when turning. I have added preload to the shocks, but don't want the car any higher, I think, at 6" frame to ground at the back of the A-arms. The tires are 205/60r13, and I'd be happy to have narrower (195/60 ought to do), but they do not seem to be available unless I go to bigger rims, say 185/60r14. The solution I am contemplating is to re-engineer the clamshell brackets to raise the fenders about an inch at the front. This could be done by either rebending them, or cutting and welding in a riser section between the light and the fender. Since I assume this is not an entirely unknown problem, what are your recommendations? I am not looking for lap times, but like a loose car on the the local twisties at reasonable speeds.
Bruce

[perry]

This won't answer your question but have you considered running without front fenders?
My front-end lift problem was cured by removing the fenders.

[magnusfeuer]

Every now and then I run into fender / stanchion contact with the tires. In these cases I either put a spacer between wheel and hub, or simply bend the stanchion to a more forgiving position.

I agree with perry about the lift issue. Even with cycle wings, a Caterham reportedly has 150 lbs of front lift at 100 mph. That lift is made much worse by the traditional fenders, which also has the downside that you cannot see your left wheel when you are about to kiss that perfect apex.

/Magnus F.

[GWise]

Personally I like the look of the clamshell fenders. It's part of the charm of the original S2 and S3 cars, dispite the lift. In order to run in many vintage organizations, cycle wings are not allowed, so I'll continue to run them on my Lotus 7.

If you look at 10 different original lotus 7s, you will see 10 different mounting positions and shapes of clamshells. The brackets are quite flimsy and there's a good chance they've been bent before. Mine have been modified from the original location to reduce drag (per scca regs)

To me the options seem pretty obvious:
Bend or alter bracket
Fit smaller tires
Adjust shock compression or go to stiffer springs
Get creative

[Mojoluthier]

I have found a seller of 185/60r13 tires in two flavors. Both are less than stellar, but are H rated and are priced right at around $50 per. Opinions are hereby solicited, particularly if it is a flat out known mistake to consider them. One is a Nexen CP 641, and a bit better looking but entirely unknown to me, the other is a Federal SS 595. Bear in mind that I do intend to drive the car recklessly, but not to win any races. Given the modest power of my car (perhaps 120 HP at a guess) the 205's really do seem like overkill, but what do I know? I CAN spin both wheels in first gear with little effort.

A more careful investigation of the rear wheel fender clearances revealed that the rear end in not centered in the car by about 1/2 inch, cause the left wheel to protrude too far, and it it the problem in the back. So I went in and adjusted the rod that locates the rear end side to side only to discover that if I center the rear end and wheels to the chassis, the differential housing and the U-joint come into hard contact with the vertical member of the frame defining the entry to the shaft tunnel. This development amazes me as surely the car was originally built this way, and the rear end is what I believe to be the standard of the day, a Ford Timken Mk2. While smaller tires will get rid of the symptom, in the rear they will not solve the real problem. I am currently contemplating cutting out the offending frame piece and welding in a similar bit a 1/2 inch of so to the right. It is hard for me to believe the car has been like this for nearly 30 years and no owner has ever addressed this issue. My disbelief causes me then to think perhaps I have misdiagnosed the problem, or that my solution is flawed as it doesn't look like it would be more than a days work to implement it. The hardest/scariest part being (to me) removing the aluminum panel behind the seats to get at the frame bit, and then re-riveting after the the welding.

Unless dissuaded by knowledgeable persons, I currently think I will get the tires for the moment, and do the frame job as an off season project.

Edited to mention that the Shop The did my diff set-up (successfully!) in Sonoma is Kampena Motors, the local Caterham connection, a one man operation owned by Rich Kamp, and I am loving the place.

[JohnCh]

Personally, I'd fit the Toyo RA-1 which is available in that size. Very sticky tire, and the sidewall is a little softer than the Toyo R888, which is another option. In the past, I've found TiresDirect.net has the best prices for Toyo, but TireRack also carries them these days.

Regarding the rear axle issue, it's definitely the axle not centered on the frame, rather than the body not centered on the frame, correct?

-John

[Mojoluthier]

Regarding the rear axle issue, it's definitely the axle not centered on the frame, rather than the body not centered on the frame, correct?

-John

The flanges on the axle housing that take the trailing links are flush to the frame on the right side, and overhang the frame 9/16" on the left side. To my eye, the frame and body are straight and symetrical. As a guitar maker, I flatter myself in believing I have a good eye for this kid of thing. Rich Kamp thinks the axle may be twisted out of line in th car, but I think his eye is being tricked by the asymmetry of the diff nose, which IS off center to the right of its housing. I am imagining that the car was originally built for an axle with a symmetrical differential housing, which mine is certainly not.

The Toyo offering is described as a track/competition tire, which seems like more that I need, not to mention being 3x the price. . . . . did I mention I'm a guitarmaker? ? ? ? TireDirect has only one RA1 in stock, apparently.

[GWise]

It sounds as though you have a panhard rod and not the standard A frame used in the lotus super 7.

Sorry - I'm not familiar with the pre-lit westfields, but I thought they were almost exact copies of caterhams which do have A frames. I question whether your diff is actually a timken as well.

I agree it sounds as though you have a asymmetrical axle in a car that was developed for a symmetrical car. Every time the suspension moves up or down with a panhard rod, the whole axle shifts relative to the body. This is one thing to consider when adjusting that panhard rod. It may be that someone just got very tired of dealing with cracked/broken/leaking axle (caused by the loads placed onto the axle every time the car encounters a one wheel bump and roll) and decided to fit something else.

To add a note about RA1 - yes they are pretty expensive. On a 7 though, they tend to be a fantastic street tire once they're warm and so long as they stay dry. The will wear out faster than normal tires, but they will also last a lot longer on a 7 than they would on anything else and grip until they cord. If you enjoy spirited drives and crave grip, they are highly recommended. Some people find tires that are a bit harder with less grip to be more "fun" to drive on, however.

[Mojoluthier]

I think the car is more a copy of a Lotus series 2/3 than a copy of a Caterham, according to my reading. It definitely has a Panhard rod, and I am relieved to hear you call it that as I have been and someone "corrected" me recently. The Panhard rod is as close to level as I can imagine, and as long as it could be, so I think it could not make more than a 1/16" difference side to side movement in the suspension's full travel (which is pretty modest compared to my motorcycles).

I believe my recent diff rebuild was done according to Timken specs with Timken parts, so if it isn't one I am truly wandering in the woods!

[Mojoluthier]

Photographic evidence!

I have some experience posting pictures in guitar forums, and have watched plenty of people fail in their early attempts, so let's see what happens here! I haven't seen ANY pictures bigger than thumbnails here, so I hope I am not violating any rules should I be successful. The first pics are the diff alignment, in the tunnel.






And here are the left and right sides showing the unbalanced reveal:




Then a shot from the rear which shows the wheels off center in the fenders:


And finally a show-off of the guitar in my tiny garage:


I am increasing confident that my analysis is correct, and thank you for your input. I doubt my neophyte welding will be any worse than what I see in these pictures!

[GWise]

The caterham rear A-frame is the same design as the lotus A frame.



It is the right axle - but attached is the shot of my series 2 showing the a frame. Even still without the A-frame, it's odd that the tunnel is so small. I think your suggested solution should work. If the panhard rod is level, you should be able to move the axle all the way to the right and the axle will swing left under bump and extension

[MHKflyer52]

Hi Bruce,
Just a thought but have you measured from the rear to the lower frame at the bulkhead on both side to see if the rear is straight to the bulkhead. In the 1st photo you posted the rear looks to be not square to the frame but maybe that is just an illusion of the 1st photo.

[Mojoluthier]

I did some measuring, and I am convinced that the car is straight and symmetrical, it is simply that the tunnel is too narrow for the hardware. I found a picture of that part of another prelit in the county of orogin, and it appears to be at least an inch wider at the rear of the tunnel! Well, the seven has always been a work in progreess!

I installed Kumho KH17 175/70r13's all around, and now only have contact on the right rear fender, and only in the most extreme circumstance.

I have bought some 1x1 tubing, and will practice welding it before I do the real work.

I also found both the drums and the rotors to be less than true, and have dealt with the drums. It is amazing that $20 a pop handles that! Next the rotors, a bit more trouble to get out of the car.

The bench seats are ridiculously unsupportive, or perhaps I am insufficiently masochistic to own a seven. Anyway, I took a bunch of EPS foam and shaped a seat bottom that fit me, glued it down to a piece of plywood, padded it with a little further shaped rebond foam, and sewed a Naugahyde cover for it. All of that was new ground for me, but the results are wonderful. Next time they may even look good.

[Mojoluthier]

Not pretty, perhaps, but the weld goes all the way through. This will move the tube over 3/4" and still connect to the triangulated point in the bulkhead frame. At this point I have a solid 15 minutes welding experience, at the outside. Thank you, Martin, for suggesting the welder I got, it couldn't be better for my purpose . . . as far as I know.