Rear caliper bolts

Good morning,

I am fitting my rear calipers and the new fixing bolts supplied by one of the major lotus parts suppliers are hitting the disks. The bolts (drilled for the locking wire) are 1 1/4" long. Should there be a washer? There is no mention of one in workshop manual and unfortunately I don’t have the braking section of the elan parts list. I could fit spring washers, but they should not be needed if the bolts are wired.

Thanks in advance,

Cheers.

My parts book shows them…

Mine are fitted with washers as well. See pic.


It’s actually been scientifically proven that spring washers mostly cause bolt looseness rather than prevent it! They may be of some help where there is something compressable being clamped (eg. a soft gasket) but not needed elsewhere. Key thing is to get the clamping load correct by tightening to the correct torque

Usually modern cars do not use spring washers anywhere!

That parts diagram is the front caliper which does have lock washers, no washers shown on the rear caliper parts list. Front caliper mount is steel and rear is alloy, that may be why one has lock washers and the other is wired.

Indeed! Sorry, I was not paying close attention when grabbing the picture.

Thanks for all the quick replies. Can I conclude therefore there are no lock or plain washers, and my bolts just are too long?

When I replaced the ones on my Elan, a prior owner had used longer bolts and lock washers, so seems a reasonable conclusion.

If the bolts will fit with a plain washer, then use those, tighten to the correct torque and lockwire.
If the bolts are too long, grind them down far enough.
It’s all part of the ‘nothing new fits’ Lotus experience.

Lock washers or plain washers in this application is good engineering practice. You are fastening a relatively high torque loaded bolt head against a relatively soft aluminium surface. A washer will prevent the bolt head digging into the aluminium.

“A washer will prevent the bolt head digging into the aluminium.”

Only if the washers used are hardened washers. Standard hardware store or AN washers are too soft.

Like the head bolts.

I used to often see hung up in workshops a cartoon which depicted a masculine bolt chasing a feminine nut that was shouting “not without a washer!”. I used a lock washer on the caliper not for it’s locking but because its smaller diameter fit the space; a standard washer being too large.

I never used the lockwire on the Elan - Schnorr washer + a dab of thread lock and never had any issues.

Current Evora uses only threadlock on the caliper bolts - no washer of any sort

Hi,
I use a thick flat washer on my car – as already stated you don’t want to damage the aluminium mounting face also with a washer you should get a higher clamp force.
Despite being the best / correct method I wouldn’t use any thread lock as it can bugger up threads especially in aluminium – our casting are expensive and rear calipers particularly so.
In the past I have always wire locked but whenever I have checked the torque they have always been good - don’t bother anymore, but I do check regularly.

@Donels have you got the right bolts on the lower arm to strut? – the heads look very big.

Regards
Steve

Well they’re standard bolts, the right length and diameter. So unless Lotus have special bolts for this application!

Hi,
I guess Plus 2 must be different to +0 Elan - maybe that’s why they went with different rear hubs?

Regards
Steve

standard in thread but must be of the proper grade I would think…

@ Donels,

Maybe the angle, but the male tube nut looks like its bottomed out where it enters the rear caliper, I use a long tube nut fitting (same length as the OEM flexible brake line, when tight I normally see a few threads.

V

I’ve used a steel washer with loctite on the bolt thread and no wire locking. I believe the difference between front and rear regarding wire locking is that the front mounting is steel, same as the caliper, while the caliper at the rear is secured to the alloy lugs on the strut which has different rates of expansion with temperature. Not worried about using loctite on these bolts as the bolts thread into the steel caliper body.