Front wheel adjustment

I have been speaking with my mechanic and steering specialist about the apparent heaviness in the steering of my TA21 DHC compared with that of my TC21/100 Saloon, and he asked about the tyres that were originally fitted to the car in 1953. He then went into great detail to explain the differences between Cross Plies and Radials with particular reference to, and the importance of the tyre profile. At this point, all I could offer was my understanding that the original tyres were 6.40 X15, or perhaps even 6.00 X 15, but I could not find any information regarding the profile -- without which he could not provide me with the proper information. I have found an old cross ply tyre in the loft, but all this shows is 6.40-15 4 Ply Rating. It is an Australian made tyre and has the numbers P204. 8062-2 and E 13505-3&A   He also requested information on the Toe in, Toe out, Camber and Castor. Can anyone help me with this information?   FYI, I currently run with Kuhmo 185.80 R15, although there has been a suggestion that I would be better using 185.65's. Many Thanks, Phil. Posted by pdadd 08/03/2015 15:30:16

Phil  Tracking should be 1/8 toe out & camber1° (wheels lean inward at the top).   I checked all this out on my TC108/G recently because the front tyres are wearing on the inner edge. Everything was smack on and no discernable wear was found on the king pins so the conclusion we reached was that the wear is attributed to modern 185 tyres being slightly fatter than the original cross-ply.  Cheers  Angus Posted by Angus D'Arcy-Drake 09/03/2015 10:02:40

Philip re Tyre profile ,I believe a straight 185X15  is  close to 6.40 ,there is no profile as the height and width are the same ,the Longstone tyre web site has lots of info on this, I think they do cross plies if you want to be original. re Steering geometry, all 3 litres seem to be the same ,alignment is 0-1/16" toe out,camber is 1*, castor is 1.5* and king pin inclination 9*.To set the alignment you only alter the central track rod,do not touch the outer ones which should be the same length (13.5" ball joint centres) and   may have had their locknuts welded to discourage adjustment. This data is in the handbook.I don't think you can alter the camber/castor angles,and the upper wishbone fixing brackets are slotted which theoretically enables you to alter  king pin inclination if you are brave.(2 of the 4 nuts are hard to reach and it is easy to shear the corroded studs)  Peter Posted by Peter Martin 09/03/2015 13:30:00

Thanks Angus and Peter, it seems that the adage " when in doubt, read the instructions" certain comes into play here. In addition to checking the adjustments, I intend replacing the front suspension rubbers at the same time. I am still open to opinion regarding the tyres. In the back of my mind I have this thought that if Alvis had wanted the TA/TC series to run on 6.40 x15 tyres (or their now  Radial equivalents), would they have not fitted these from the start, and not chosen 6.00 x15's? I have found a contact here in Sydney who is of similar age to mine and still has a hands on interest in his tyre business. My question to him will be; if 185's are the equivalent to the 6.40 tyre, would it not be preferable to fit 180's which are listed as the equivalent to the 6.00's? Thanks again for your input. Posted by pdadd 10/03/2015 03:22:45

Philip,  Firstly I would not entertain fitting 185 65 radials. The motor revs will rise sharply on the highway as the tyre is too small. It won't look right either.  With respect to aspect ratio for the cross ply it is probably 98 or 95. At about the time the TA21 was produced tyre manufacturers were experimenting with fraction sizes, hence 6.40 instead of the standard 6.00 or 6.50 the latter two having a 100 aspect ratio.  The correct radial is 185  80. My car is fitted with Firestone 6.40  15 tyres and they are very good. Tyre pressure is between 28-30 psi. As per the road reviews of the day, the steering does require constant correction. Radials tend to sit better at speed and likewise with cornering. The cross plies do make slow speed driving easier, especially parking.  With respect to wheel alignment I prefer a setting of zero toe with a slight bias towards toe in. I find this to be the best overall compromise.   Richard Melbourne Posted by RichardWallach 10/03/2015 03:43:00

Philip,  I forgot to offer a comment re the suspension bushes. It pays to also replace the upper bolt (C5840) and the tubes (C5851) as well. With respect to the bolt it may have to be cut in order to remove it if it hasn't been done in the past. The steering box is in the way. The bolt can be fitted in the other direction without issue. I found the tubes to be very worn and if reused would have chewed out the new rubber bearings. Chris Prince sells a complete kit. Worth investigating.  Be warned it is a "cow" of a job. Use a good quality spring compressor. I prefer one that fits in the space for the shock absorber and therefore works from within the spring rather than one that compresses from the outside. You may have to add a few thick washers in order to fit the opening.   When removing the bottom shock absorber mount check its placement as the bottom mounting hole is a little offset in order to allow for up/down movement without the shock absorber rubbing on the spring.  Richard Posted by RichardWallach 10/03/2015 04:31:09

Correction  The outer track rod ball joint centres are 13.25"  NOT 13.5" as I previously posted  Apologies  for any confusion  Peter Posted by Peter Martin 15/03/2015 15:39:20