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Split rim Compomotive rebuild - Suspension/Brakes/Wheels/Hubs/Steering/Geo - The Lotus Forums Jump to content
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Split rim Compomotive rebuild

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After recently re-building my Compomotives I thought TLF readers would be interested in the journey. It was a great side project and has given my split rims a new lease of life. Most wheel restorers stay clear of split rims due to the labour involved. I found the process relatively simple which gave a huge sense of accomplishment once complete, here we go!

 

Disclaimer: This personal perspective in the refurbishment of my Compomotive split rim wheels. Visitors who use this information do so at their own risk.

 

Tools required

10mm spanner

5mm allen key

Parallel punch

Torque wrench (that can torque to 26 ft lbs)

1 tube of mastic sealer and applicator gun                                                                                          

Spray and polishing equipment dependent on level of commitment

Vernier gauge

6mm allen bolts. 12.9 grade steel. 40mm length. Quantity, 80

6mm flange nuts, Quantity, 80

Aluminium ‘hat’ washer, black anodised. Quantity, 80

 

As you can see my wheels were looking quite sorry for themselves and were leaking air. Once the tyres are removed you’ll have a better idea of how they are built up. These 3 piece rims consist of a rear barrel (inward facing of wheel closest to the suspension/brake components), centre piece and front rim (outward facing). It’s a good time to inspect the wheels as they stand. Check for cracks and dents in the rims and spin them on the front axle of your car to see if they run true. It will give you a chance to evaluate if they are suitable for rebuilding. I’m unsure of where to find replacement barrels or rims. Luckily mine were all serviceable.

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Before separating you have to unbolt 20 nuts and bolts per wheel. I preferred to loosen off the nut on the back side in case your spanner slips. To reduce pressure off the rims evenly I undid the fixings at opposites. Imagine looking down at the back of the rim, using the numbers on a clock I would undo 12 ’o’ clock, then 6 ’o’ clock, 3 ‘o’ clock, 9 ‘0’ clock etc and work my way round until they are all removed. I would also advise not to throw anything away. Keep all parts even if broken just in case you require them for reference at a later time.  

 

When the nuts are off, gently unscrew the bolts and their aluminium washers out from the front rim. You may need to tap them through from behind using a parallel punch or an old bolt.

 

Before separating, consider adding some centre punch marks on the inside of the rims and wheel centre to reference the position of each part relative to each other. I didn’t bother as I felt the parts would not have been manufactured to such high tolerances originally.

 

Originally the wheels had rubber O rings for a (not so!) air tight seal. It allows for an easier disassembly but I still had to use a hand trowel, lightly tapped between the barrels and wheel centre to break them apart. An old kitchen knife is another useful tool for separating the edges. Using a screwdriver is too localised and blunt, possibly leading to damage if you tried to drive it into the groove too hard. If the wheel has been rebuilt before it might have mastic sealant around the inside that will need picking off/dissolving before separating.

 

Once apart you have several options on refurbishment depending on time, skill and funds available.

 

Previous Compomotive wheel threads mention the rims were originally anodised. My understanding is the process can only be performed on ‘new’ metal with an even surface finish. Due to tarnishing over time mine were not suitable for re-anodising. I like most owners chose to polish up the rim instead. You might feel confident enough to paint/polish the components yourself.  I chose to outsource the wheel polishing and painting to local firms. I cleaned up the rear barrels myself but resisted painting them for reasons that will become apparent...

 

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Several weeks later I received my powder coated centres and polished rims. Upon trial fitting them I noticed the barrels didn’t sit in the original recess. On closer inspection I noticed the tight tolerance between the centre and the rim. Powder coating is quite thick and made installation of the rims impossible. The mating faces between the wheel centre and barrel must be flush to ensure a wheel that runs true.

 

To rectify the problem I used a sanding block with 300 grit paper to sand back the powder coating and level off the mating face back to metal  so the rims would sit comfortably against the wheel centre. A Dremel was employed to sand paint off the wheel centre edge, returning a gap tolerance to the rim. I measured it with a Vernier gauge to ensure even thickness all round. At this point it’s advisable to thread some new bolts through and have a dry run assembling the wheel to check everything lines up correctly. Once satisfied with the fitment of each wheel I masked off the centres and lacquered the exposed metal is give some corrosion protection.

 

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When my wheels were split the only signs of fatigue I found was on the aluminium ‘hat’ spreader washer. Several of these washers had fine cracks through them and the original black anodising had worn down. I tried sourcing a replacement set from Compomotive but they said they no longer stocked them. Undeterred I drew up my own ones and have made a batch myself! I work in the automotive industry as a digital modeller so I managed to get a limited run built. Let me know if you require a set for your rims.

 

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Once you’ve had a dry run checking everything fits together you’re ready for reassembly. I attempted 1 wheel at a time, you’ll be tightening 80 nuts and bolts in total, take your time! As mentioned before, Comopomotive originally sealed the wheels with a rubber gasket to varying levels of success. I am not aware of anyone offering these seals nowadays so as an alternative I used black mastic bought from a local hardware store. I filled the back groove with the sealant using an applicator gun, carefully laying a continuous bead. This face was then laid onto the rear barrel with 4 bolts inserted to ensure correct alignment.

 

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Attention to detail is essential at this stage. If you look closely you can see parts of the groove that didn’t have sufficient mastic to seal against the rim. I subsequently found out this wheel leaked when the tyre was fitted.

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The front face was then given a bead of sealant and the front rim was attached. New bolts and washers were threaded through the wheel in preparation to torque everything down. I used 12.9 grade steel allen bolts that have a high tensile strength (size M6 x 40mm Socket Cap Head screw). This part of assembly was carried out in quick succession to ensure the mastic was still ‘wet’ to give an air tight seal.

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On the back of the wheel I chose to apply a 6mm nut that had its own flanged base. You may prefer to use regular nuts with a washer. Each nut should be secured with thread lock. Each thread received a nut tightened by hand.

 

I have looked online to find the correct torque settings for these rims. This link recommends a torque setting between 26-28 ft lbs:

 

http://www.edition38.com/forums/index.php?showtopic=127763&page=1

 

 I used a similar assembly technique as mentioned earlier, torqueing opposite the rim each time to spread the load evenly. I took them all to 10ft lbs first, then 20 ft lbs and finally 26 ft lbs. To ensure all wheels were torqued correctly I laid masking tape on the inside rim and ticked them off as I went along!

 

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During the powder coating process the wheel refurbishers noted the centres were quite porous (the paint bubbled up as they heated the wheel to bake the powder coating). To help ‘seal’ the wheel I spread the mastic that had squeezed out to cover the centre section.

 

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Just a thought I work with a guy who repairs and welds alloys we get loads of split rims in and we never add sealant to the rim when it's apart it won't seal properly clean the surfaces mate them together once bolted up tight put the wheel onto a rotation device a front hub or a machine will work . Then run masking tape around the barrel and lip leaving a gap about 2 cm either side of the join then turn the wheel and add sealant on top of the join turn the wheel rim and smooth over with your finger till the joint it flat to the top . Then whilst wet peal off the tape this will give the sealant a nice uniform edge .leave to dry for at least 24 hours before adding the tyre and inflating . Very important ! 

Then when inflated the Sealant pushes into the hole and cannot pass through ie no air leaks . Never put sealant in the joint like a gasket it doesn't ever work.

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Great thread, thanks for sharing. I had one leaky wheel but that was cured with a new o-ring. Now I have four Compomotives that hold pressure which is a rare and wonderful thing!

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Thanks for the comments, I hope the community finds it useful in their endeavours.

The sun was out today so I took a few more pix, enjoy!

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Jo

what a superb thread. When I get on my computer [instead of this stupid ipad] I will be in touch about some washers and compomotive stickers. 

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Glad you like the thread Phil. I hope my parts can help keep your Compomotives pristine!

Here is another pix of the washers, if you compare the old with my new ones you can see how I designed them slightly thicker which will hopefully prevent them from cracking. 

 

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Regards

Jo

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Jo

Having a few days away so limited computer access. Will be in touch. I'm only in Bury st Edmunds.  Might come and have a look at yours if you don't mind

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Hi Phil, you're welcome to come over...if you bring your dry sump! I'll PM you with my details in the coming days.

 

Jo

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Curious as to how you have these on an 86 car. Did you replace the hubs, suspension links etc?

 

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Hi Andy, the car came with the Compomotives. A previous owner fitted them by modifying the hubs to accept the 4 stud wheels.

Last year I met a chap that owned the car in the 1990's. Back then it ran on the regular BBS multi spoke alloys. A lot easier to maintain but I am glad to have the Comps. I'll post some pix of the car when it's finished in a few months time...

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THAT is how it's done!

Great to see another Turbo on Comps, must be the only black one around like this.

The pictures say it all!

Magnificent!

:thumbup:

Fingers crossed you're bringing it to MBW on Sunday.

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Thanks Jonny, I took inspiration from the Autoart 1/18th scale Esprit most of us have. I always wanted an Giugiaro Esprit Turbo on comps. I think I'll struggle to get to MBW next weekend but will hopefully catch up with the TLF posse later in the year.

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Yes I have the same model, nice to have the full size version to go with it!

I also wonder where Autoart got their inspiration from, particularly for the white and red car which also featured gold Compomotives - unlike Roger Moore's FYEO car which had powder coated black centres as per the Essex cars. It can't be that all the Autoart cars had gold wheels because the Autoart Essex had silver and black wheels.

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Thanks for all the kind comments. They'll be fitted to my latest restoration, I'll post the journey in the coming months...

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Awesome looking esprit,  those comps will look stuuning on that motor !  are you going for ski racks also :)  You defo need the goodyear glue on letters for that car for the tyres even more so with it soon to wearing comps :thumbup:


A

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Hi Dan, I have a set of Goodyear NCT's that will be going on with white lettering, de rigueur of course! Not interested in the ski racks though.

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