15" wheels

[French Frie]

Ok... Update ! For once, the weather was shiny yesterday, and I wanted to swap my wheels... I started by the rear ones, without any problem, even though there is less than 2 cm between the exhaust line and the tyre  (but I assume it's not a problem, right ?)
   
   But things are different for the front [:(]... As a member already told me, the steering arm is fouling with the inner rim, and wheel can't even turn (see pic) ! I thought that the Hawk/compomotive was made for the MKIV, and this was a part of my decision vs the Trigo...
   
   
   
   So, I had to put the 16" wheels back, and now need to find a solution : either bending the steering arm to clear the rim (geo needed and maybe more weakness) or having a spacer made (but will the pegs be long enough) ... 4 or 5mm should suffice.
   
   For those who have choosen the Hawk wheels: did you encounter the same issue, and what was the option choosen ?
   
   It's a pity, because it does look good withe the 15", and a quick test with the rear ones fitted showed a very good grip ...
   
   

[French Frie]

In addition to this post, does it mean that AKLs have different steering arms ?
   
   Just to show the difference ( diameter and ET) vs 16" :
   
   

[SJ351]

I believe you will find thay are the same and bent at the factory to suit the smaller wheel diameter. One of the ex Autokraft fitters told me this a few years ago.

[B.P.Bird]

Olivier, Bending steering arms sounds horrific, but it isn't. All the competition cars had bent arms in period. I have bent a few in recent years and it is not a problem:
   1) Although it can be done in situ I would remove the complete steering arm /calliper carrier.
   2) Mount carrier end in a sturdy vice. Be sure of the orientation - do not bend in the wrong direction....
   3) Use an oxyacetylene welding torch and heat the arm gently at about half way along the arm to a uniform cherry red over about 1" length.
   4) Apply some gentle muscle, via a suitable pipe, bending the arm inboard.
   5) The early cars had about 1/16" clearance to the rim, which looks scary, but works fine. Do not bend more than necessary as you do not want to run out of adjustment on the track rod.
   6) When you have the first one done make the second one look the same. Absolute precision is not essential as the track rod length will be adjusted to regain the correct tracking - refer to Graham Stuart for the correct Mk.IV settings. I think they are on a thread here somewhere.
   7) In period it was usual to bend arms to such a degree that all of the adjustment was used up and then the track rods had to be shortened and longer threads cut. Judging from your photographs you do not need this amount of bend.
   Courage mon braves

[French Frie]

thanks Barry !
   
   those were the days, my friend [;)] !  I must say that it concerns me to bend those arms ... regarding the geo, I did it few months ago and posted here the datas.
   I'll try to make spacers before going this route... but thnaks for the info !
   
   PS: just for your knowledge, "mon brave" is a bit paternalistic (or implies subordination) in French... don't say it to someone who serves you here, or he can be upset (anyway, french people are upset by everything [:o)]!)

[B.P.Bird]

Olivier, I would not use any spacers when there is a tried and tested solution available. Perhaps I have made it sound more complicated than it is.
   My apologies for misuse of the French language.

[French Frie]

Barry, it sounds clear and precise, thanks ! Regarding SJ351 did it on his car , and it is a common modification on other cars... I have to determinate yet what is the required thickness ( few millimeters, me thinks) by putting some washers on the pegs and measure their total thickness... If a too thick spacer is required, then I'll explore the bending arms solution!
   
   For the language mistake, please do not apologize... It was funny [;)] !

[B.P.Bird]

Olivier,
   Fitting spacers to a peg drive hub, even if thin, is perhaps a risk. The torque will now apply a bending rather than shearing force to the pegs and this was not how they were designed. How much torque goes through the pegs and how much through the mating surfaces and tapers is a question quite beyond my amateur engineering.....
   If you must use spacers then drill and tap the wheel and use counter sunk screws and maybe adhesive to ensure that the spacer becomes part of the wheel. I have done this as a second best solution when finding wheels that were not machined for a Cobra hub, i.e GT40 wheels, in the days before Trigo.....

[French Frie]

thanks Barry... not sure to see the issue, but anyway... I tried this morning with shims to figure out what would be the thickness of the spacer, and even with 6 millimeters thickness, it still touchs the rim! the wheel now turns, but it's too narrow... and with that space, the spinner is not inserted enough :( ! it's not cute, and it's not safe !
   
   so the bending option is now number one ... but once again, I'm very surprised and disappointed that those Hawk wheels don't fit, as they were supposed to do so ! I would curious to try Trigo wheels and see the difference ...
   
   I looked at the rod ends, and there is about 1,5 cm (0,6 inch) of thread left, so it should be enough to compensate the bent arm... hopefully the rod end can go all that way !

[cobham cobra]

I had a set of the Hawk wheels and Avon tyres fitted to my MkIV last year and I, like most people, had to have the track rods bent to make it all work. The guys that look after my car said they have to it virtually every time an owner has gone 16 inch to 15 inch (Hawk) wheels. I also had to have the mating face of the wheels machined to match the hub in order to get the correct fit, but all in all it was no big deal.
   As Barry said, it's what they did in period.
   John.

[B.P.Bird]

I do not believe that it is possible to fit 15" x 7.5" front wheels to a leaf spring or coil spring chassis without bending the steering arms (sometimes having to shorten the track rods.) Even in the period where fronts were only 6.5" the arms were modified. I do not believe there is any difference, in this respect, between Hawk or Trigo wheels. I suppose it is possible that there are wheels somewhere with less inset, but I have not come across them and in any case you would then have clearance considerations outboard i.e wheel arch bodywork fouling the tyre.....
   At least Olivier your exercise in packing out the hub with washers gives you a good idea how much to displace the ball joint eye on the steering arm when applying your muscles.

[cobham cobra]

Sorry, but I wrote rubbish the other day. The machining of the new 15 inch Hawk wheels was to get the correct fit with the spinner and not the hub.

[SB7019]

I must be the lucky exception as my change to 15" has left the track rod end/steering arm just ( and I mean just) clearing the rim.  Like many others I find the 15" vastly superior to the 16" and since having had Big Al fit a front anti roll bar and working his magic on the settings the car is an even greater pleasure to drive.

[Paul Mundy]

Like Peter my superblower`s track rod ends/steering arms only just about clear the rim without modification. My front rims are Trigo however.

[wenzeh]

I had purchased a new pair of track rod ends / steering arms when I did the restoration on AK 1005 and the parts where straight / without bending.  Therefore I believe that the left / right hand part will receive its final form in a second step bending procedure.  Bending procedure was provided also as written before, however I got the advice that the parts should receive a polished surface prior to bending in order to avoid cracks.  Hope this helps.