Need Input: Wheel Offset / Spacer Questions

lookforjoe

True Classic
The new wheels I bought (Rota Kensei) are wider in the rear than the ones I have from Vic's - 9" vs 8", both zero offset.

I needed 1.5" spacers for the 8" wheels. Before I order new spacers for the wider wheels, to make sure the overall track is the same, I wanted to get others opinions on my math - which sucks in general.

I am assuming that I need to move the new wheel in by .5" (since they are zero offset) to achieve the same track as I have currently. So, I would need to order 1" spacers to replace the 1.5" I'm using now.

Does that sound like a reasonable calculation?
 

carl

True Classic
I have 8" wide wheels on my X (205/60/13 tires) and didn't need any additional spacers. How about using a stack of stock spacers (doesn't everyone have 10 or more of those laying around) to figure out what size you need?
 

lookforjoe

True Classic
I have 8" wide wheels on my X (205/60/13 tires) and didn't need any additional spacers. How about using a stack of stock spacers (doesn't everyone have 10 or more of those laying around) to figure out what size you need?
Like this?



I didn't think I would need to go that route, car is on jack stands, etc. not easy to raise & lower to check things at the mo :D

This is what I have from Serpent auto for the Vic's wheels I don't want to remachine these, since I will then be stuck if I want to switch back :)



I'm going to assume zero offset really means zero offset & get 1" hubcentric spacers with the 4x98 to 4x100 bolt pattern shift for the Rota wheels



I may end up having to do something with the back brakes to make them pretty like the new fronts

 

rachaeljf

True Classic
Track is measured between the wheel centre lines, so moving each wheel in by half an inch will reduce the track by an inch. I guess you want to keep the overall width across the tyres the same, so moving each wheel in by half an inch would be correct if you are also using one inch wider tyres as well. If you are keeping the same size tyres you may not need to change anything.
 

rx1900

1981 X1/9
The new wheels I bought (Rota Kensei) are wider in the rear than the ones I have from Vic's - 9" vs 8", both zero offset.

I needed 1.5" spacers for the 8" wheels. Before I order new spacers for the wider wheels, to make sure the overall track is the same, I wanted to get others opinions on my math - which sucks in general.

I am assuming that I need to move the new wheel in by .5" (since they are zero offset) to achieve the same track as I have currently. So, I would need to order 1" spacers to replace the 1.5" I'm using now.

Does that sound like a reasonable calculation?

No, no Hussein !!! If both wheels have the same OFFSET....then your track will remain exactly the same !!! No need to change spacers or anything like that.

The tread of the tire will be in exactly the same place as before. No further out - or in. No difference there. The only difference will be that the BEADS of the tire will now be spread out a little more. The outside and tread will remain in the same location.
 

rx1900

1981 X1/9
Hey Hussein. By the way.....please dont tell me you are running those new 9" wheels front and rear....

And what tires are you putting on the new wheels ?? Sure hope they are a lot wider than the 205 and 225 you were running before.....
 

kmead

Old enough to know better
So if you are trying to maintain where the outside of the rim and the face of the tire is in relationship to the fender lip, then yes a 1/2” thinner spacer will be needed.
 

Dr.Jeff

True Classic
I'm with Karl and Rachael. I believe what Doug said is not what you were asking and therefore incorrect in this case....unless I am the one that is misunderstanding your question.

The way I interpreted your situation, you wish to maintain the actual location/dimension of the outer lip/edge of the wheels/tires relative to the fenders...i.e. they will look/fit the same overall width (as the old ones) relative to the bodywork. To do that your initial calculation was correct. This is also assuming the wheel manufacturers dimensions are accurate. I've found a large inconsistency between wheel makers when it comes to stated measurements. So you might want to actually get the new wheels in hand and check the true dimensions before ordering any spacers.

Also remember the inside edge of the wheels will be 1" further inward; .5" due to the wider wheel + .5" due to the narrower spacer. Be sure you have enough suspension clearance for that.
 

lookforjoe

True Classic
UOTE="kmead, post: 337747, member: 204"]So if you are trying to maintain where the outside of the rim and the face of the tire is in relationship to the fender lip, then yes a 1/2” thinner spacer will be needed.[/QUOTE]

Damn. Yers, that was the point, I got side tracked. I have no room for the wheel to sit further outward. What Doug was saying is that the bead will move out 1/2", with the sidewall stretched compared to the 8" wheel, since I used the same size tire, the only change is the wheel width. I'm not sure now whether it is an issue or not. I've already ordered the spacers. If they are too wide, I'll just machine them down. Can't go the other way & add, so I'll see how it goes.



there is room for 1" inset - plenty of room by the strut, which is the closest member

IMG-20191116-152243.jpg
 
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Dr.Jeff

True Classic
Rota has some great wheel styles for a small company (relatively speaking when it comes to wheel makers). They seem to focus a lot on variations of vintage designs, which I love - particularly for older car models. These will look great on your modified X. ;)
 

lookforjoe

True Classic
Hey Hussein. By the way.....please dont tell me you are running those new 9" wheels front and rear....

And what tires are you putting on the new wheels ?? Sure hope they are a lot wider than the 205 and 225 you were running before.....
Only 9" in back, fronts are same 8" as existing. Tires are the same


 

Ulix

True Classic
To recap: when using the same size tire on the 8" and 9" rims, the contact patch of the tire will remain in exactly the same position.
The edge of the rim will stick out further and the side wall of the tire will be shaped differently, will be more "stretched".
But since it is the contact patch of the tire that is usually relevant to fit and look, I would stick with the same spacers as before.
 

carl

True Classic
The point with the stacked spacers is you get the actual spacing rather than driving yourself crazy with the math.

The wheels look beautiful. Just don't weigh your new wheel/tire combo and then compare them to a 185/60/13 tire on an iron cross rim!
 

Dan Sarandrea (Phila)

Waitin' On Parts...
Not that there is much you can do about it, but I wouldn't want to be a stock rear wheel bearing on a car with significantly wider track + 150% increase in tire patch + 250% increase in horsepower + "spirited" driver.
 
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