I got a pair of 15x8.5 aluminum slotted rims and tried them on the back over drum brakes and it seemed like 10cm outside of the body. I saw few of you wear 15x8 on the back. Which seems too wide as well.
So my question is - when you do drum to disk brake conversion, does the track width become more narrow? And if so - how much more narrow? Or I'm missing something?
Don' know if it helps but I believe the track width actually increased slightly, but the amount would depend on the offset of the rims. Also, I think the original size wheels were 6" wide so 8" with the same offset would widen the track a bit too.
Neilvermilion said
May 15, 2023
1965CS wrote:
Don' know if it helps but I believe the track width actually increased slightly, but the amount would depend on the offset of the rims. Also, I think the original size wheels were 6" wide so 8" with the same offset would widen the track a bit too.
But I believe you have 15x8 on the back, right? Do you happen to know what's a back space on yours by any chance?
4SPEED427 said
May 15, 2023
I don't know if you've seen Mark's thread on the 65 and up B body conversion but there may be some info in it to help you.
Now I did, thanks! However it brings more questions:) So his setup makes that track width value higher, which kinda eliminates possibility to have 15x8s with roughly 4 inches BS on the back. Is 15x7 the widest option for after disk brake conversion?
-- Edited by Neilvermilion on Monday 15th of May 2023 04:31:17 PM
1965CS said
May 15, 2023
Neilvermilion wrote:
1965CS wrote:
Don' know if it helps but I believe the track width actually increased slightly, but the amount would depend on the offset of the rims. Also, I think the original size wheels were 6" wide so 8" with the same offset would widen the track a bit too.
But I believe you have 15x8 on the back, right? Do you happen to know what's a back space on yours by any chance?
i used to have 15 x 8 on the front too with 255/60 tires but didn't like the steering feel. Changed to 15 x 7 and 225/70 to match diameter. Don't recall the offset of either.
-- Edited by 1965CS on Monday 15th of May 2023 06:05:13 PM
cdnpont said
May 15, 2023
Oleg, I have Wheel Vintiques Series 62's 15x7 4.25" BS front, 15x8 4.25" BS rears on the 65 Laurentian.
Went with a 69-70 single piston disc conversion on the 65. Akerman fix as well on the 65,(67 and up Center link, Pitman, Tie rods and idler ).
Using C3 Rotors with 69 drum brake hubs. Track increase of about 1/8" each side. A 15x8 with 4.25" BS would have fit no problem up front. Chose a 7 and 8" wheel for the offset look. The 8" fits under the wheel lip on the back, but not a ton of room left.
4.25" backspace is what you want. Maybe 4" tight on the back depending on the tire section width, but I don't think any less than 4.
Gillis said
May 16, 2023
If its on the rear it will become wider. The thickness of the disc brake rotor is wider than the thickness of a brake drum, and they mate up to the axle surface which doesnt allow for any movement inward. It is what it is. Front conversions are usually the same width as stock.
-- Edited by Gillis on Tuesday 23rd of May 2023 06:31:21 AM
1965CS said
May 16, 2023
Neilvermilion wrote:
But I believe you have 15x8 on the back, right? Do you happen to know what's a back space on yours by any chance?
Found the specs on my set;
15 x 7" Bolt Circle: 5-4.75" Back Spacing: 3.75"
15 x 8" Bolt Circle: 5-4.75" Back Spacing: 4.5"
seventy2plus2 said
May 16, 2023
I'm not clear if you're looking to put discs on the front, rear or both.
Neilvermilion said
May 16, 2023
Both
seventy2plus2 said
May 16, 2023
Neilvermilion wrote:
Both
Rear discs is a lot of expense with little gain. Most of the braking is done with the front wheels.
cdnpont said
May 16, 2023
A 15x8" wheel with 4.5" Backspace should readily work with a rear disc conversion. Any less and you are probably into the WW lip. The rotor hat thickness on a conversion isn't likely to be over 7/16 thick.
I say this with the thinking being that I have 4.25" backspacing on a 8" wheel with a 245/60/15, and there is still a wee bit of clearance. And remember, a drum is near a good +3/16 thick on the axle anyway, so you still have that in the equation.
So keep your tread width reasonable, add a 1/4 backspace, and then take it away with the hat thickness.
I'd like to see you take a backspace measure on those slotted wheels. 10CM past the bodyline is confusing to me. Has to be a smallish backspace on a 8" wide Wheel.
Neilvermilion said
May 16, 2023
Yeah, I kinda messed it up with my calculations:) Backspace on those 15x8.5s is 3 and 3/8
-- Edited by Neilvermilion on Tuesday 16th of May 2023 07:34:49 PM
cdnpont said
May 16, 2023
What rear disc brake setup are you planning to run Olaf?
Neilvermilion said
May 16, 2023
I'm just planning to purchase one of those completealll wheel bolt-on disk brake conversion kits for Impala 65. I believe you were saying 11 inch would be the one. They go for around 2k.
-- Edited by oshawacliff on Wednesday 17th of May 2023 01:29:14 AM
rebelrouser said
May 21, 2023
I installed an all GM JL8 Camaro 4 piston caliper 4 wheel disc brake setup on my 'Chief. Esee peesee...........Everything was C3 except for the JL8 e-brake cables.
jonathanD said
May 21, 2023
I used c3 corvette rear brakes on my 67 i followed rebalrousers advice im running a 15x10 corvette style rally with a 285/65r15, rolled the fender lips, had to make some Clearance aswell,
So... It gets more funny. Now I got 15x7.5 rims instead of 15x7 (was convinced they are 15x7 by seller and rushed by angry wife to buy faster). The back space seems to be almost 4", maybe 3 3/4. So now on the back if the rim is mounted I have around 1cm in between the rim projection line and the body...
Now my question is - does the tire wall goes wider than the rim border projection? If so - how far? Am I safe now or I should stop buying used things on Facebook?:)
Hey guys,
I got a pair of 15x8.5 aluminum slotted rims and tried them on the back over drum brakes and it seemed like 10cm outside of the body. I saw few of you wear 15x8 on the back. Which seems too wide as well.
So my question is - when you do drum to disk brake conversion, does the track width become more narrow? And if so - how much more narrow? Or I'm missing something?
Cars 1965 Parisienne CS
Thanks.
Don' know if it helps but I believe the track width actually increased slightly, but the amount would depend on the offset of the rims. Also, I think the original size wheels were 6" wide so 8" with the same offset would widen the track a bit too.
But I believe you have 15x8 on the back, right? Do you happen to know what's a back space on yours by any chance?
I don't know if you've seen Mark's thread on the 65 and up B body conversion but there may be some info in it to help you.
Corvette rotors for big disc cars. - Canadian Poncho (activeboard.com)
Now I did, thanks! However it brings more questions:) So his setup makes that track width value higher, which kinda eliminates possibility to have 15x8s with roughly 4 inches BS on the back. Is 15x7 the widest option for after disk brake conversion?
-- Edited by Neilvermilion on Monday 15th of May 2023 04:31:17 PM
i used to have 15 x 8 on the front too with 255/60 tires but didn't like the steering feel. Changed to 15 x 7 and 225/70 to match diameter. Don't recall the offset of either.
-- Edited by 1965CS on Monday 15th of May 2023 06:05:13 PM
Oleg, I have Wheel Vintiques Series 62's 15x7 4.25" BS front, 15x8 4.25" BS rears on the 65 Laurentian.
Went with a 69-70 single piston disc conversion on the 65. Akerman fix as well on the 65,(67 and up Center link, Pitman, Tie rods and idler ).
Using C3 Rotors with 69 drum brake hubs. Track increase of about 1/8" each side. A 15x8 with 4.25" BS would have fit no problem up front. Chose a 7 and 8" wheel for the offset look. The 8" fits under the wheel lip on the back, but not a ton of room left.
4.25" backspace is what you want. Maybe 4" tight on the back depending on the tire section width, but I don't think any less than 4.
If its on the rear it will become wider. The thickness of the disc brake rotor is wider than the thickness of a brake drum, and they mate up to the axle surface which doesnt allow for any movement inward. It is what it is. Front conversions are usually the same width as stock.
-- Edited by Gillis on Tuesday 23rd of May 2023 06:31:21 AM
Found the specs on my set;
15 x 7" Bolt Circle: 5-4.75" Back Spacing: 3.75"
15 x 8" Bolt Circle: 5-4.75" Back Spacing: 4.5"
Rear discs is a lot of expense with little gain. Most of the braking is done with the front wheels.
A 15x8" wheel with 4.5" Backspace should readily work with a rear disc conversion. Any less and you are probably into the WW lip. The rotor hat thickness on a conversion isn't likely to be over 7/16 thick.
I say this with the thinking being that I have 4.25" backspacing on a 8" wheel with a 245/60/15, and there is still a wee bit of clearance. And remember, a drum is near a good +3/16 thick on the axle anyway, so you still have that in the equation.
So keep your tread width reasonable, add a 1/4 backspace, and then take it away with the hat thickness.
I'd like to see you take a backspace measure on those slotted wheels. 10CM past the bodyline is confusing to me. Has to be a smallish backspace on a 8" wide Wheel.
Yeah, I kinda messed it up with my calculations:) Backspace on those 15x8.5s is 3 and 3/8
-- Edited by Neilvermilion on Tuesday 16th of May 2023 07:34:49 PM
What rear disc brake setup are you planning to run Olaf?
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-- Edited by oshawacliff on Wednesday 17th of May 2023 01:29:14 AM
I used c3 corvette rear brakes on my 67 i followed rebalrousers advice im running a 15x10 corvette style rally with a 285/65r15, rolled the fender lips, had to make some Clearance aswell,
i was willing to make a few relief cuts
Im about half an 1/2 inch Wider face to face
So... It gets more funny. Now I got 15x7.5 rims instead of 15x7 (was convinced they are 15x7 by seller and rushed by angry wife to buy faster). The back space seems to be almost 4", maybe 3 3/4. So now on the back if the rim is mounted I have around 1cm in between the rim projection line and the body...
Now my question is - does the tire wall goes wider than the rim border projection? If so - how far? Am I safe now or I should stop buying used things on Facebook?:)
Just do this
-- Edited by Gillis on Tuesday 23rd of May 2023 06:37:50 AM