Wheels, tyres and diff ratios

[jonclancy]

Hi Everyone,

I was having a look around past postings on the WSCC forum for info on MEMFast and found the following post from TonyL in the Members Offers section...misfiled!

http://forum.wscc.co.uk/forum/index.php ... ven-tyres/

Tony asks:

Posted 09 May 2007 - 08:59 AM

Mark
Can you plse confirm the tyre sizes you are using on your current Eleven demonstrator.
I am still having wheelarch clearance problems at the front, using Pirelli P3000 165/80 X R13 T on Minilites. The steering lock has to be severely restricted to avoid rubbing, and I have had to modify the headlamp housings to prevent the tyres fouling them and also the lamp wiring where it enters the housings.
I do not recall having such severe problems when driving your previous demonstrator, and am thinking of reducing the tyre width and profile at the front.
It may also be that the Minilites have a greater offset than the Minators you are using, making the problem worse. Any thoughts would be welcome.
Thx.

Now I'm running the car, I'm getting used to this lock restriction - but it has caught me out a couple of times. On the open road it's fine, but I have to plan every junction if I'm not going to run out of lock. The rack locks are metal sleeves and so will need dismantling for changing. I have notice a small amount of rubbing on full lock in reverse.

The Minilites fitted are MA1350B, 13x5, ETO - ET26

I was wondering what size steel-wheels and tyres otherw were running, whether the rubbing is a a problem, how much lock you have and finally (for interest), what diff ratio you are running, please?

I find that cruising round the Cotswolds, I use 4th, a bit of an event over 60 MPH and just 3rd for 30 MPH, and feet that a slightly longer diff might help. I am running a 3.9 though. Anyone out there with a 3.7 care to comment whether performance is blunted at all?

Cheers

Jon

[Westfield 129]

I am running minitors on one of my cars, with 185/70/13 tires (still readily available from most manufacturers, and perfectly suited to the 5" rim width), and no steering restricting lock at all. Sure, it will rub at full lock, but it is easily corrected by simply dialing out a little steering. I have no problems driving around the city and making U turns (actually easy if you just punch the throttle in 1st or 2nd, as it will spin in place).

My wheels have a backside spacing of about 3 7/8". If you have less backside spacing (easily measured), then you will have additional problems with rubbing at full lock. You can specify the backside spacing with some manufacturers, so do some checking prior to buying wheels. Don't worry about "offset". Instead, rely on the simple to measure "backside spacing" that will give you a direct measurement as to where the outside inside of the rim will fall. Too easy, really. Quick tip: Generally, a wheel for a front wheel drive car will have a deeper backside space. This might help. Also, the Minitors and the Minilites can be orded in the same backside spacing. If you can, get the wheels that Westfield supplies with the kit. Simple fix.

Fact is, the Lotus 11 had problems at full lock as well, with the front wheels being fully enclosed. Just the nature of the beast. I no longer worry about it and I have over 55K miles on my car.

If a lock is fitted, it is fitted only to one side of the rack, as one side is restricted by the location of the pinion gear. You can figure this out by simply turning the wheel, and noting the tire position.

I would just take the locks off, as this is a quick and easy fix.

If you have problems with the lamp wiring, you have the wrong size front tires, or you need to space the headlights a little forward on spacers under the buckets. Also, use side exit plugs, rather than rear exit plugs, to keep the wiring out of the way.

I have built several cars with 15" wheels, and have no problems clearing the lighting with 4.50X15 front tires on wire wheels used for Triumph TR3 or MGA in 4.5 or 5" widths.

Currently, I am running a 3.9 final drive with my 13" wheels, with a Datsun B210 5 speed transmission. I cruise at 80 mph, 3700 RPM. All day long. I have plans to mount the 15" wire wheels on my own car, but will probably switch back to the 4.22, and keep the same 3700 RPM. I don't want to lose the acceleration with those tall (5.00X15) rear tires. My Datsun transmission does have a shorter first gear than the old 4 speed ribcase, and it would cruise at 90 at only 4000 RPM, but I would lose the snap that the car currently has at the bottom end, and the 0-60 in 6 seconds.

While you can go to a 3.7 final drive ratio, the best setup is a 3.9 and the 5 speed if you are running the 13" wheels. Better if you order a "long 1st" T9 transmission from SP Components.

[jonclancy]

I've only got a few mins to reply, so it'll be short - but thanks for the info, Jan

Your tyres are wider and therefore taller than mine, so I suspect it's the backside spacing. Can you just elaborate on the "outside inside of the rim", please? Deeper backside space = wider track?

I may contact WSC for more details of the Minators, shame to change cos my Minilites are minty!!

Sounds like the 210B has a long gear set.

TTFN

Jon

[erictharg]

I run rack stops as specified in the build manual (machined from nylon barstock and fitted over the rack bar) and run both 5" and 5.5" 13" rims with no fouling. It does give you restricted lock but only noticeable when doing parking type moves. No fouling on headlight shells - they are fitted from the front of the clam as opposed to from the back face. Not sure what difference that makes.

[Westfield 129]

Backside space is the space at the BACK SIDE of the wheel. From the rim outer edge to the wheel mounting face. Easy to measure. Just put a straight edge across the wheel, and drop a scale or tape measure to the flat mounging face and read off the measurement at the straight edge across the wheel lip. It is best to do this without the tire on the rim, as you may have to guess at the measurement with the tire in the way.

The narrower the backside spacing (smaller measurement), the farther out the outer edge of the wheel is, the wider the track. You are looking for a measurement of around 3 13/16" to 3 15/16" (around 96~100mm)

Measure the backside spacing of your curreent minilies. It is probably close, and you may be able to have the mount face machined as much as .25" to increase the spacing and narrow the track.

My tires are wider, but shorter, or the same height. 185/70/13 is about the same as a 165/13, give or take a .1" or so.

I also run 15" wire wheels.

I would remove the rack stop and see what you have for lock with the bodywork in place. Drive the car.

[jonclancy]

Great - long reply typed and hotel internet disconnected at the wrong time and lost my posting.

So, in short:

A tyre comparison tool says that 165/80 is 19mm (.74") wider in diameter than 175/70.

My locks are metal tubes around the steering gear, so I would have to dismantle the rack to remove them. Will leave that for later otherwise I might miss a gap in the rain to go out driving.

Can anyone give me the part number or exact spec of their Minators, please? Also, what tyre sizes are you running, Charles?

Thanks for all the info so far.

Jon

[erictharg]

I started out with 165/70 x 13 Avon CR322's on an old set of Ebay sourced 5 x 13 Avon safety wheels. No fouling whatsoever on the road or hillclimbing and trackdays. Currently running (same size as Jan does) Yoko A021 185/70 x 13's on 5.5 x 13 Compomotives (can't recall the offset but not more than 10mm different to stock Midget). Good for me for several reasons. Great wet tyre for racing (very soft - lots of grip) but road legal E makred tyres. Only about £50 each from Polley as they are the control tyre the stock car guys run. Plus a useful (on the road anyway) increase in gearing over the 165's as bigger diameter. They look big on an Eleven but again no fouling at all (using the W/Field spec rack stops). And because the Eleven is so light I can also get away with racing on them in the dry. A true "do everything" tyre. I'd recommend them for the road. Unless you want lot's of movement and sliding at road speeds in which case go with whatever size of CR322's you favour. As a "high fuel economy tyre" they have pretty low grip. Fun on track days...

[jonclancy]

Hi Charles,

Thanks for the info. I'm amazed to see I can get a set of four 175/70R13 CR322 delivered for £133!! I may give them a try to see if that improves the fit.

ATB

Jon

[Westfield 129]

The only way to fix the problem is to change the rack stops.

185/70 is the best combination to use with the 13" wheels, but it does improve grip to a point where you have to be going quite fast to get a nice drift. More like an S type or Caterham than the original W11. Even inexpensive tires in this size will give amazing handling, and good transition to over steer.

[jonclancy]

Hi Jan,

Please can you elaborate? If I would like to get a bit drifty at lower speeds, would the 175/70 CR322 be a slightly better bet? They are unbelievably good value, it has to be said!! If there is little differerence, I would try the cheaper tyres. I assume the 175 profile will give me a little more lock as well.

I'll be looking into Haynes for the work required to get these stops removed and then jack up the front and test for clearance limits.

All good advice here, thanks for that!

Jon