Considerations for converting a 26" DS to 27.5"

[Re::Cycling]

Happy Monday Morning hubbers,

 

I've been considering a 26" -> 27.5" conversion on a DS, and have been reading up a bit about it here:

 

https://community.bikehub.co.za/topic/118476-275-inch-650b-wheels-on-a-26inch-frame/ 

https://community.bikehub.co.za/topic/132949-conversion-of-26-giant-anthem-x-to-275/

https://community.bikehub.co.za/topic/137613-carbon-frame-conversion-to-275/)

 

Wanted to find out what factors affect the conversion. From what I've read, these are the main things to look out for (correct me or confirm):

• Fork compatibility / spacing
• Rear triangle compatibility / spacing
• crank arm length - going to slightly larger wheelset means the crank is a bit higher, so might want to put on a slightly longer crank for better stability in technical bits.

Been trying to find resources on whether the fork / frame I have will work for this setup, and finding mixed answers. Sounds like tyre width might be an issue too depending on clearance (seen guys talking about being restricted to 2.00 width, restricting the 2.25 tyres). Wondering if a bit of number juggling would work for determining this:

 

Radius of a 26" wheel:

2 x Pi x r = 26"

r = 13/Pi = ~4.148

 

Radius of 27.5" wheel:

2 x Pi x r = 27.5

r = 13.75/Pi = ~4.376

 

Difference in radius is about 0.229", or about 6mm, so if the minimum clearance all around (fork / chain stays / triangle) with 26" is 40mm - 50mm before narrowing then the conversion should be easily possible, right?
 

 

 

[RABUBI]

Best forks:

- Lefty

- FOX

- Rock shox Sid

 

I used to have a Scott spark 30 and Also a Chinese carbon frame I converted. Both worked perfectly

 

https://community.bikehub.co.za/topic/147018-keeping-my-26-training-bike-alive-since-2008/

[Captain Fastbastard Mayhem]

Happy Monday Morning hubbers,

 

I've been considering a 26" -> 27.5" conversion on a DS, and have been reading up a bit about it here:

 

https://community.bikehub.co.za/topic/118476-275-inch-650b-wheels-on-a-26inch-frame/ 

https://community.bikehub.co.za/topic/132949-conversion-of-26-giant-anthem-x-to-275/

https://community.bikehub.co.za/topic/137613-carbon-frame-conversion-to-275/)

 

Wanted to find out what factors affect the conversion. From what I've read, these are the main things to look out for (correct me or confirm):

• Fork compatibility / spacing
• Rear triangle compatibility / spacing
• crank arm length - going to slightly larger wheelset means the crank is a bit higher, so might want to put on a slightly longer crank for better stability in technical bits.

Been trying to find resources on whether the fork / frame I have will work for this setup, and finding mixed answers. Sounds like tyre width might be an issue too depending on clearance (seen guys talking about being restricted to 2.00 width, restricting the 2.25 tyres). Wondering if a bit of number juggling would work for determining this:

 

Radius of a 26" wheel:

2 x Pi x r = 26"

r = 13/Pi = ~4.148

 

Radius of 27.5" wheel:

2 x Pi x r = 27.5

r = 13.75/Pi = ~4.376

 

Difference in radius is about 0.229", or about 6mm, so if the minimum clearance all around (fork / chain stays / triangle) with 26" is 40mm - 50mm before narrowing then the conversion should be easily possible, right?

 

Don't rely on the number jogging, the best solution is to use a 650 tire and wheel in your preferred width and tyre, and see if it will fit. A 650 is not truly 27.5" unless you get (i think) a 2.25" tire, and even then they have different volumes and dimensions so best is to just experiment. 

 

But yes - if your clearance atm is 40-50mm then it should be easy. Just check to see if the front & rear will touch anything under full compression. Deflate front & rear suspension, and check where the wheels are at max copression. If you have an inch or more to spare, you should be fine. 

[Re::Cycling]

Manitou R7 carbon fork + Merida Multivan frame

[Re::Cycling]

Don't rely on the number jogging, the best solution is to use a 650 tire and wheel in your preferred width and tyre, and see if it will fit. A 650 is not truly 27.5" unless you get (i think) a 2.25" tire, and even then they have different volumes and dimensions so best is to just experiment. 

 

But yes - if your clearance atm is 40-50mm then it should be easy. Just check to see if the front & rear will touch anything under full compression. Deflate front & rear suspension, and check where the wheels are at max copression. If you have an inch or more to spare, you should be fine. 

 

Thanks captain, will give it a bash.

[vaalkol]

Happy Monday Morning hubbers,

 

I've been considering a 26" -> 27.5" conversion on a DS, and have been reading up a bit about it here:

 

https://community.bikehub.co.za/topic/118476-275-inch-650b-wheels-on-a-26inch-frame/ 

https://community.bikehub.co.za/topic/132949-conversion-of-26-giant-anthem-x-to-275/

https://community.bikehub.co.za/topic/137613-carbon-frame-conversion-to-275/)

 

Wanted to find out what factors affect the conversion. From what I've read, these are the main things to look out for (correct me or confirm):

• Fork compatibility / spacing
• Rear triangle compatibility / spacing
• crank arm length - going to slightly larger wheelset means the crank is a bit higher, so might want to put on a slightly longer crank for better stability in technical bits.

Been trying to find resources on whether the fork / frame I have will work for this setup, and finding mixed answers. Sounds like tyre width might be an issue too depending on clearance (seen guys talking about being restricted to 2.00 width, restricting the 2.25 tyres). Wondering if a bit of number juggling would work for determining this:

 

Radius of a 26" wheel:

2 x Pi x r = 26"

r = 13/Pi = ~4.148

 

Radius of 27.5" wheel:

2 x Pi x r = 27.5

r = 13.75/Pi = ~4.376

 

Difference in radius is about 0.229", or about 6mm, so if the minimum clearance all around (fork / chain stays / triangle) with 26" is 40mm - 50mm before narrowing then the conversion should be easily possible, right?

 

2 x Pi x r is the formula for the circumference of a circle with radius r.

 

The radius of a 26" wheel is 13" (diameter/2)

The radius of a 27.5" wheel is therefore 13.75" (nominally)

[Re::Cycling]

2 x Pi x r is the formula for the circumference of a circle with radius r.

 

The radius of a 26" wheel is 13" (diameter/2)

The radius of a 27.5" wheel is therefore 13.75" (nominally)

 

Oh right, used it as a circumference measurement, not diameter. Thanks for picking that up.  The difference in clearance is actually just under 20mm between the 2 wheel sizes.

[Eugene]

Just a question..............how would a longer crank give you more stability in the technical bits?

[popcorn_skollie]

Yea  I wouldn't even bother with math on this one.

I ride 26. My front tyre claims to be 2.5 width.

But when I measure it. Its just shy of 2.3

What Cap said really is the best option.

Try the wheels and check the clearence if you manage to squeeze it in.

[popcorn_skollie]

Just a question..............how would a longer crank give you more stability in the technical bits?

 

I think he has a point. Longer crank arms may offer a slight advantage on berms when holding down your outside foot. But descending with pedals level which is pretty much most of the time. Crank arm length won't change anything to combat you slightly higher bb.

Edited February 2, 2015 by popcorn_skollie

[W Smith]

Best forks:

- Lefty

- FOX

- Rock shox Sid

 

I used to have a Scott spark 30 and Also a Chinese carbon frame I converted. Both worked perfectly

 

https://community.bikehub.co.za/topic/147018-keeping-my-26-training-bike-alive-since-2008/

Converted my Scalpel size small nearly 2 years ago to 27.5 and gave it a new lease on life. Clearance at the back is an issue. Ideally  I  have to run a 2.0" tyre at the back .At the moment I have    a 2.1" Crossmark at the back and at R220.00 at CWC you can not get a better deal. The Vredestein Spotted Cat at 2.00" should also be an option. As for the Lefty fork there is plenty of clearance and you can fit any tyre. A friend of mine converted a S Works hard tail which had a lot of clearance at the back after the conversion. It all depends on the frame and fork . I took my bike to Janos at Evobikes to test fork and frame compatibility before I bought the wheels. I suggest that you do that.