Beachcomber's 940 Estate project

[jamesy12345]

70 mm spacer sounds a lot..good site below for comparing effect of different offsets

http://www.willtheyfit.com/

Internet says 940 wheels were 25 offset & those jag wheels 61 offset. so a 40 mm space would bring the face of the jag wheel out 4 mm further than stock ones. I looked for some info on spacers increasing scrub radius vs handling also, not for scare mongering just for some thoughts on it.

http://rennlist.com/forums/racing-an...-handling.html

[beachcomber]

70 mm spacer sounds a lot..good site below for comparing effect of different offsets

http://www.willtheyfit.com/

Internet says 940 wheels were 25 offset & those jag wheels 61 offset. so a 40 mm space would bring the face of the jag wheel out 4 mm further than stock ones. I looked for some info on spacers increasing scrub radius vs handling also, not for scare mongering just for some thoughts on it.

http://rennlist.com/forums/racing-an...-handling.html

I've been down this road before - there are obviously at least two different offsets / backspacings for various Jag wheels of that era.

Without question - mine measure 72mm back space. I based my original billet blank order on the info listed on some sites.

The reason for ordering the larger thickness blanks is so they can be machined down as required with a "Hubcentric" flange. At this stage, I'd rather have them too thick and machine to size !

However, my car is hopefully coming back from the workshop today, so all the guesswork can be remedied this coming weekend.

BTW - "scrub" is measured using the CENTRE of the tyre as one referrence point. That is only altered by the width of the tyre within the wheel well. The other referrence is the "Steering Axis Inclination" - which is fixed. Don't blame me for the inacurate [ NTS ] drawing I whizzed off the internet - the "centreline" on the right hand drawing - obviously isn't ! But that's the general idea.

Thanx for everyone's input.

[jamesy12345]

I've been down this road before - there are obviously at least two different offsets / backspacings for various Jag wheels of that era.

Without question - mine measure 72mm back space. I based my original billet blank order on the info listed on some sites.

The reason for ordering the larger thickness blanks is so they can be machined down as required with a "Hubcentric" flange. At this stage, I'd rather have them too thick and machine to size !

However, my car is hopefully coming back from the workshop today, so all the guesswork can be remedied this coming weekend.

BTW - "scrub" is measured using the CENTRE of the tyre as one referrence point.

Thanx for everyone's input.

Fair enough about the machining down, I was thinking you were adding a 70 mm spacer somewhere....hence was thinking scrub radius would be increased if on the front - https://en.wikipedia.org/wiki/Scrub_radius
Scrub radius is changed whenever there is a change in wheel offset. For example, when the wheels are pushed out from the body of the car the scrub radius becomes more positive

(or a more long winded reference Competition Car Suspension by Alan Staniworth.....3rd edition available on the net - search for "Competition_Car_Suspension.pdf")

ps can you see CH 60 stamped on the back of your wheels somewhere - that should mean offset is 60

http://bmwused.com.mx/rines-jaguar-s...r831007ba.html

[beachcomber]

Fair enough about the machining down, I was thinking you were adding a 70 mm spacer somewhere....hence was thinking scrub radius would be increased if on the front - https://en.wikipedia.org/wiki/Scrub_radius
Scrub radius is changed whenever there is a change in wheel offset. For example, when the wheels are pushed out from the body of the car the scrub radius becomes more positive

(or a more long winded reference Competition Car Suspension by Alan Staniworth.....3rd edition available on the net - search for "Competition_Car_Suspension.pdf")

ps can you see CH 60 stamped on the back of your wheels somewhere - that should mean offset is 60

http://bmwused.com.mx/rines-jaguar-s...r831007ba.html

Thanx for your continued input.

To be clear - I'm talking about the "BACKSPACE", not the offset. The backspace is the only measurement that is of any interest to me as that determines the spacial position of the wheel and the clearance to any restrictions - struts, wheel arch lip etc.

I know the Staniforth book [ and Alan ] very well, I have a 1st edition personally signed copy in my library.

All will become clear [ or not ] in the coming weeks when I can physically check the car against my wheels!

[jamesy12345]

Thanx for your continued input.

To be clear - I'm talking about the "BACKSPACE", not the offset. The backspace is the only measurement that is of any interest to me as that determines the spacial position of the wheel and the clearance to any restrictions - struts, wheel arch lip etc.

I know the Staniforth book [ and Alan ] very well, I have a 1st edition personally signed copy in my library.

All will become clear [ or not ] in the coming weeks when I can physically check the car against my wheels!

Yes understood about the backspace it is easier to measure than the offset. If any use I have a spreadsheet of the calcs in Chapter 8 of the book mentioned, I was using it to work out different corner loads depending on anti-roll bar thickness

[beachcomber]

Just collected the car from 5 week's hibernation having MOT and various bits done. What a pleasure to drive. I had a direct back to back comparison as I drove up to my pal's workshop [ 10 miles ] in my V70 [ which I left there for a service ] and 30 odd miles back - just for the hell of it ! The 5 week delay was no fault of my pal BTW.

Thanx for the offer of the spreadsheet - but as stated - I have an original signed copy of Alan's book in my personal library. I also did a lot of the original "string computer" work when Alan was devloping his "Terrapin" race cars.

I've decided to go ahead and get the -40mm Killen springs and Bilsteins fitted [ all round initially ], then I'll start in earnest on the wheel swap. I know peeps have fitted up to 9" wide wheels on the front - so I know my 7.5"s will fit.

[jamesy12345]

...
Thanx for the offer of the spreadsheet - but as stated - I have an original signed copy of Alan's book in my personal library. I also did a lot of the original "string computer" work when Alan was devloping his "Terrapin" race cars.
...

OK fella no probs I meant a Microsoft Excel file with all of the load transfer formulae so you can input your own numbers to complement the book. Sounds like you have no need

[beachcomber]

Hey .................always learning !

The first 50 years just gives you the groundwork !

[beachcomber]

After several delays the car is now fitted with the -40mm Kilen springs and Bilstein dampers and I'm collecting it from the workshop tomorrow with a 13 month MOT.

Then I'm off for a short chill break to Saxony and on my return it's full steam ahead.

First job is to FINALLY measure the available space from the hub face and the Jag wheels so the spacers can be accurately determined and I can get them made. Rears are not a problem - just a case of placing the wheel spacially to fill the wheel arch up, so the billets I already have will do for that [ I have 40mm and 50mm]. That just leaves the front to be determined.

Insured today [£135 Fully comp ] so I will be putting my V70 Auto on the market soon and using the 940 full time.

BTW - the "-40mm" springs actually yield 1 3/4" at the front and only 3/4" at the back. Looks OK, but another 1" or so would be better !