Spring & Dampers

[Westfield 129]

The problem with the Westfield's bushes is that they literally shear... Tear apart, leaving no rubber at all.

They are not really designed to be tightened. They do a good job of isolating vibration, but are not very good if the center element is required to turn. There is simply not enough rubber, only about 3/32". It destroys itself in a very short period of time.

Since I do use my car on long tours, and drive to and from the track for testing and timing sessions, I have found that putting the car on the ground, ballasting it and then tightening up the bushings as recommended, just results in a destroyed suspension in a very short period of time, and very dodgy handling.

One day, I just loosen everything up, and the difference was incredible. The chassis floated over bumps, and grip was much more predictable. The additional advantage is that the rear bushings started to last much longer. I can now get about 2000 miles out of a set of rears before the rubber is simply extruded from the shell.

The problem is that the thin rubber bushing, when mounted in the rear suspension, gets pulled and twisted during normal driving (part of the normal operation of the bind inducing 4 link setup). Body roll, acceleration and braking all conspire to rip the bushing apart. It can't really survive more than a few hundred miles before failure. It's worse in the early cars without the shear plates to support the rear suspension arm bolts at the chassis end. These plates can be added, by the way. Anyway, not requiring the center sleeve to rotate within the rubber greatly increases the life of the rubber element, as it is no longer being ground away between the rotating center element and the outer shell. If the rubber shears, it's no longer a bushing. It's a bolt, rattling around inside the old bushing shell.

Why I am presented with the argument about rotating elements and shear in the bushing as being good things is beyond me at this point. Lots of owners have tried rose joints in the suspensions, no rubber at all! I did that, but found that the usual binding of the 4 link was hard on the affordable rose joints. The good ones cost nearly $900 for the 10 necessary to equip the rear suspension, and I can buy a lot of rubber bushings for that. What would be problem be with allowing the bushing to rotate? Well, nothing, other than better handling, and increased bushing life. The bushing acts as a vibration damper, which is fine. It allows for some compliance in the bind prone 4 link, which is a very good thing, indeed. The bushing can rotate about the suspension bolt without damaging anything. Just make sure that the bolts are properly greased when installing the bushings. The reality is that even the best chassis only gives about 2000 miles from the rear suspension bushings. At that time, at least one pair will need replacing. One on an upper rear suspension arm, and the diagonally opposite lower arm. Shortly after that, you will replace another pair...

If you have 9000 miles on your bushings, I am sure that they are gone. Remove the suspension arms, and the rubber will fall out. If you put the car in gear, remove the rear body, and rock the chassis against the engine's compression (roll the tire, do not set the hand brake), you will see the rear axle rotate, and hear the clunk of the suspension arms. This is especially evident with the early chassis. The late chassis can hide the failure, as the rubber is trapped behind the shear plate. You have to check for loose bushings by rocking the chassis front to back.

I have had this argument with many before about the Westfield's little suspension bushings. What I know, is that they fail quickly if tightened. A failed bushing that is tight doesn't control the rear suspension at all, and it clunks and bangs around. Don't tighten them, let them rotate in the chassis, and they will last much longer, and properly locate the rear suspension arms. The reduction of static friction in the chassis will make it track and handle better in all conditions. Try it. I have put 10s of 1000s of miles on mine without problems, but with much longer bushing life, and far better handling and ride. The little Westfield bushing is not like others, as it has so little rubber. Even the factory has reduced it's torque specification for the bushing to 24 lb.ft.

The main thing to think about is bolt retention. Use new Nylocks, or castle nuts with cotter pins.

The front end bushings last longer as they are not twisted during suspension motion. However, the benefits of reduced friction (looser setup) are undeniable, and the bushings will last longer there as well. You will be surprised as to how well the W11 rides when the bushings are not clamped down.

About the anti roll bar. The chassis has lots of roll, you just are not aware as your eyes are about 28" above the road. Turn a corner, and hit the throttle. You get wheel spin, as that inside wheel has followed the body and is not really in good contact with the road. The ARB will help here, but not much. Stuck with the high roll center, your best bet is an LSD, specifically a clutch type, though a Quaife type may work. The clutch type always works.

Dampers are important as the ones supplied with the cars are so poor in quality and damping ability. The late chassis don't even have the right size dampers installed, and may have rear springs that are too stiff.

Get rid of the 2.25 dampers and springs in the front! The original design called for 1.75" dampers and 1.9" springs. This will give you an inch more front end travel (you can start with dampers half an inch longer, at least, as the hats wont be fouling the upper arms at droop. The new cars use the thicker dampers as they are available in about the right length (nearly an inch short!), and, most importantly, the right price. If you do go to another brand of damper, go with the thinner body, and teh same spring, but in 1.9" diameter. If you have an early car, you already have the small diameter dampers up front. Just keep that setup when you change them out.

In the rear, you can use anything you want. I have large diameter dampers back there, as that is what was sent by mistake.

I promise to post the proper damper lengths tomorrow.

Damper settings are to complement the driver, but there is no reason to have a damper stiffer than is necessary to control the springs/chassis. The idea is to produce grip and predictability. When doing race car or hot road car setup, we look for damper control. Sometimes, that's stiff, other times, the chassis comes out riding quite well.

One modern car that best exemplifies this is the Noble M400/Rossion Q1. Tenacious grip (over 1.1G), but the ride is actually quite compliant.

One of the most interesting things in automotive chassis development over the last decade is the improvement in dampers. It doesn't have to be stiff, and can be quite a bit faster, and easier to drive if the chassis is properly damped. Sometimes, it is not really that stiff.

One thing that I have seen, universally, with W11s here in the US is that none are at the correct ride height. They are all too low. And none have the proper toe setting in the front. Alignment shops don't do chassis setup, and can't set toe on a 1000 lb car without the driver installed.

[erictharg]

Jan - I'll check my bushes over the winter. You have far more experience of this than I do. I'll let you know what I find. I agree with you on dampers and springs - Westfield seem to have used whatever was to hand and lowest cost.

Adam - I like the idea of a test early next season. I'll have made quite a few changes to my car, so good to try them out and optimise settings before the first race. Keep me posted. Are you thinking of a pukka test day or trackday?

[erictharg]

By the way, what's your experience of the front lower upright bushes? They seem to last better than I'd have expected given they take all the suspension loads, but the bore in the Midget upright is not ideal for that brass bush to run in. I was thinking of opening it out to take a Glacier DX type bush and using a hardened sleeve between it and the bolt.

[Alan FIAT]

I was interested to read about rear suspension bushes binding. When I first got my car it was noticably twitchy at the rear. On checking the rear bushes it was clear that they were 'locking up' due to their inner and outer metal sleeves being virtually the same length, thus causing the bush outer sleeve to bind against the chassis fixing under moderate axle movement. I bought new bushes from Westfield and machined the outer sleeve back by 1/16" each side before fitting. The result after fitting has been a more progressive handling trait.
These bushes have now covered some 7000mls with the odd track day and some sprint events and still appear OK, but I will check this winter.

Alan

[Westfield 129]

With the W11 weighing only about 1100 lbs, I prefer to spring it softly to keep it from bounding from corner to corner. The W11 is not a Kart. It has suspension, and it should be utilized to improve handling and ride. Having the advantage of the light chassis means that you can use softer springs and deal with a lot less kinetic energy. Of course, the key to a softer setup is a capable set of dampers, with adjustable REBOUND control. So far, the AVOs, lacking in rebound, in the affordable, single adjustable version, are not so good in the rear, and acceptable up front (full soft in the rear, one click up front). I run enough ride height to keep the chassis in the middle of the dampers roughly 3" travel. I will post later today the correct damper measurements. The current cars run a damper that is way too short for the application, a necessity due to the large diameter front damper now used by Westfield. 'Working on a new setup for two RHD cars here, I have high hopes for the longer Protecs.

I would also try the AVO double adjustables, as they are available in precisely the correct lengths. Again, use the smaller diameter springs and dampers in the front suspension to ensure full suspension travel, and no binding with the spring hats.

My goal is to find a damper that has excellent high speed damping. One that doesn't lock at half travel due to a high force/velocity impact. This behavior is normal for most inexpensive single adjustable dampers. I am looking for a better solution that gives me the grip and predictability I want, and full rear suspension travel for some additional ride comfort and tracking around fast, bumpy corners.

I am going to run the standard Westfield bush in the front lower trunion. I have also thought about making a delrin bush with an inner sleeve as well. More on this when I take the uprights apart to check the kingpins. The last original part on my Old W11/129. I may go to the 4340 spindles with new uprights. There doesn't seem to be much of a problem with the lower trunion bushing with it's nylon inserts. Anyway, it's easy to replace, and inexpensive. Best if properly lubricated regularly. BTW, Delrin makes an excellent top trunion bush as well. Much better than the urethane bushings. The stock bushings are better than the Urethane, in fact. No problems with running Delrin on the Sprites for the last couple of decades, and there is plenty of isolation left in the front end from the standard metalistic bushings in the arms. Delrin will have to be custom made for the Westfield, as the Spridget ones don't seem to fit properly with the Westfield's upper arms setup.

[adamwilkinson]

Westfield 129

Whilst i apprieciate that you are fairly knowledgable by the sounds of things, please dont make assumptions about our car. Saying that i should ditch the 2.25" dampers for 1.9" on the front is ridiculous as you dont know anything about our car.

We get no fouling between damper and wishbone at full droop or full compression - why would i run a setup that might foul?!?

I will continue to run medium settings on our dampers along with the spring ratings i mentioned previously as this works well for me.

Do feel free to watch our car in action on youtube, search Spa Summer Classic 2010 - awracing.

Just to clear things up I'll provide a short spec list of our car.

6x13 fronts
8x13 rears
2.25" front shocks
1.9" rear shocks
Front ARB
Wilwood 4 pot front calipers
MX5 rear calipers (we run a disc conversion)
Hydraulic hand (e) brake
Well developed 1275 engine
SCCR 4 speed ribbed 'box
Quaife diff + uprated half shafts
Ultra lightweight bodywork (you'll notice the bonnet lifting in the video)
Aluminium centre section, doors, passenger cover.

Oh and the chassis and trailing arms are the only parts that are Westfield, everything else is custom.

I apologise if I've taken what you wrote the wrong way, this is the danger of written communication - i just dont like assumptions being made.

Charles, I'll keep you posted, trackdays are usually better value for money then test days, especially if you get an open pitlane day!! Test days are usually sessioned (although Mallory are usually good at giving open pitlane test days) Maybe even get a few 11 owners along for a trackday??

Anyway,

Happy Christmas to you all

[Westfield 129]

I write about Westfield 11s, their build demands, maintenance and preparation. Obviously not your car, as it is no longer a Westfield.

Any modified cars, such as plans built Lotus 11s, and modified Westfields with no Westfield suspension parts can disregard my input.

I am not making any assumptions about your highly modified car.

However, I would change the rear suspension as well. I might suggest a suspension arm change using a compliance bushing at the axle, and a rod end at the chassis. This would give you additional articulation, and enough compliance to keep the 4 link from binding.

An adjustable height Panhard Rod (jack screws at both the axle and chassis end), allowing roll center height change might be helpful as well.

My Westfield 11s Specs:

1380 BMC A W/Longman race head, 10.6:1 compression, APT Scatter Pattern Cam, Weber 40 DCOE on a 6" custom Maniflow. 125 HP @6500 RPM at the clutch. This is my road engine. 'Runs on 91 octane.

14.3 secs 1/4 mile @101 mph. No correction for temperature. It was 96 F that day.

Datsun 210 5 speed transmission

4.22"1 final drive (soon to be 3.9:1). I like to cruise at 80 mph on my way to the track, at less than 4000 RPM

TranX LSD

Race axles with splined, bolt on drive plates

AVO dampers (now leaking at 15,000 miles) 1.75 dia front, 2" rear

13X5" wheels, Cheap, no name 185/70 radials. Sticky and predictable

Taper Timken front wheel bearings

Light weight body panels (original Westfield XI panels, half the thickness of the current production)

480 Kg wet weight

Slated for wire wheels, Dunlop race tires, Protech dampers and a cosmetic restoration

Can be seen on Velocity channel," Mille Miglia" North America program

My RHD new production XI:

1380 BMC A, Longman race head, scatter pattern cam. Same engine spec as above, also 125 HP

Standard suspension components (to be changes as necessary during development)

4340 front spindles

Taper Timken front wheel bearings

15" wire wheels. 15X5 front, 15X5.5 rear. Rears are center laced. 15X4.5 front tires, 15X500 rear Dunlop Vintage Race tires

Wire wheel specific MG Midget axle housing

Double bearing rear hubs

Twin master cylinder braking system w/Westfield bias bar brake pedal

Wire Wheel race axles from Peter May

TranX LSD

Custom radiator designed specifically for the W11 chassis. Total weight, including fan 2 kg. 3X cooling improvement over the stock X flow rad

SP Components CR type 9

I will change the brakes if the chassis demands it. Porterfield brake pads and shoes

Dampers are on the development list, once the car is on the road next month.

[erictharg]

I'll be interested to hear your dimensions on dampers. I'm guessing half the problem with mine is that there's not enough droop on the rear, so it picks up the inside rear with very little roll. So, a little more droop travel is a must for the rear (although I'll have to relieve the undertray where the axle casing currently hits at full droop). The current dampers also allow the rear corners of the seat pans to hit the road before the dampers bottom out, also suggesting they are too short. The front I'm not worried about at present as it behaves fine, and the factory 350 lb springs keep it all in check. So maybe a pair of ProTech's for the rear to start with.

[adamwilkinson]

Rose jointed (at both ends) panhard rod was one of our upgrades a few years back, we also moved the mount on the axle down so that the rod is parallel to the ground when im on board (i cant remember where we heard that this is recommended).

[Westfield 129]

While it might be better to have a longer damper for compliance, the problem with lifting the inside wheel during cornering really has to do with the high roll center. Making the dampers longer wont change that, and the rear axle will still follow the body roll, lifting the inside rear wheel.

The trick is to lower the roll center.

Generally, the rear roll center is about where the Panhard Rod crosses the axle center line. Moving the axle mounting point lower will help lower the roll center somewhat, lowering the chassis mounting point as well will help more.

If the lifting of the wheel is causing traction problems, add an LSD.

Oh yes, the dampers...

Front, with a 1" bump stop installed: Extended 12.5" Closed: 9.5"

Rear, with a 1" bump stop installed: Extended 14" Closed: 10.5"

These were the measurements of the original dampers installed on my early chassis W11. I replaced them with AVOs that were 1/2" longer. This caused a problem at full droop in front, but not in the rear.

The fronts should be just the right length that on full droop, they don't touch the steering rack. You can go shorter, but not longer.

The rears can be half an inch longer. The axle wont touch the chassis. However, you may have to make a larger hole in the rear pan to clear the differential/axle center section.