7 or 8 tooth for steering rack

[265bhp]

hi all

as part of the process of restoring my 63 FHC it is being converted from LHD to RHD

I bought a used rack off ebay, described as for series 1 or 2

from the date stamp, i am assuming it must be a very late 4.2 as '71 is evident




I have noticed that this RHD rack has a different set of internals as well as some different details (much prefer the elegant profiling of the rack of my LHD original, on the right in this photo)



you can also see the difference in the profile of the spigot, the original LHD is on the right which has a slightly larger diameter spindle and different length teeth, and has 8 teeth, wheras the new RHD spindle has 7 teeth....

was this an option on the later 4.2's or standard fitment....making for a more relaxed driving..?



and by the time the later 4.2 rack was being built this lovely little identity pressing was replaced by a plain one




and here they are together, otherwise identical...(original LHD on the left this time)



so my question is whether a 7 or 8 tooth on the spindle makes much difference...I seem to have little choice if I use this new rack, unless I replace the bearing in the aluminium casing

can anyone tell me what the difference in feel might be ?

thanks in advance

regards
Jonathan

[SteveG]

Jonathon,

I would have thought that having 8 teeth on the spindle rather than 7 would make for a slightly 'quicker' steering rack, i.e. less input to achieve the same change of direction.

[265bhp]

Hi Steve

thats kind of what I was thinking too.. so I was hoping someone on the forum might have driven both types of cars and might be able to comment on the difference style

regards
Jonathan

[hastylane]

Both the rack bars look to have 23 teeth. So the the 7 tooth pinion will 3.285 turns (of the steering wheel) lock to lock and the 8 tooth pinion will be 2.875 turns lock to lock.

The 8 tooth pinion will be the faster rack with slightly heavier steering and
the 7 tooth pinion will be the slower rack, but with lighter steering.

Hope this is useful.

All the best

Andrew

[265bhp]

Hi Andrew, you are correct that they do have the same number of teeth....I wonder if it makes a noticeable difference to the feel of the car...having never driven an e type I"m out of my depth here, my only experience of classic cars is my early 911...
regards
Jonathan

[hastylane]

Hi Jonathan,

I guess the 3.8's with narrow crossplies could handle heavier steering, whereas the later 4.2 with wider tyres needed lighter steering hence the change in ratio.

Maybe a question for a specialist. Ken Jenkins at Derek Watson Jaguar will probably know.

Regards

Andrew

[PeterCrespin]

It's the same situation as swapping steering wheels - diameter changes the required effort to turn the wheel, and the degree of front wheel turn-in per unit distance input at the wheel rim circumference.

The only 'bad' options (they might be preferred option for some) would be wide rims and sticky tyres and a 14" steering wheel used with the 8-tooth pinion , or hard-inflated RS cross-plies used with a full 16" original steering wheel on the 7 tooth pinion. The former would lead to unacceptably heavy parking effort for many, whilst the latter combo might make things a little too light and insensitive at speed on twisty roads.

Other less one-sided combinations are unlikely to be unpleasant, just subtly different in the way ride and noise can vary between examples.

Pete

[265bhp]

Hi Andrew, Pete

I think I will stick to my "new" 7 tooth version, it sounds like it was developed for a good reason, and I may well end up putting ever so slightly wider tyres on the car, in which case it would make sense

thanks again

regards
Jonathan