El Mar 27.5+ bb height.

serviceguy

Well-Known Member
I finished building the 27.+ wheel set that I will use to replace the 29” wheels on my El Mar. According to my calculation going from a 29”x2.35” Tire to a 27.5”x2.8” tire will lower my bb by 7mm. Is that significant in any way? I can raise the head tube to compensate by 20mm or just leave it alone...always one more question!
 

rick81721

Lothar
I finished building the 27.+ wheel set that I will use to replace the 29” wheels on my El Mar. According to my calculation going from a 29”x2.35” Tire to a 27.5”x2.8” tire will lower my bb by 7mm. Is that significant in any way? I can raise the head tube to compensate by 20mm or just leave it alone...always one more question!

How does one raise a headtube and how would that affect bb height? I could see a longer fork
 

serviceguy

Well-Known Member
How does one raise a headtube and how would that affect bb height? I could see a longer fork
Using a special lower headset cup designed for that purpose. I have one from Wolftooth that does that. It’s like having a longer fork, instead I’m keeping the current fork and remove 20mm worth of spacers from under the stem. It doesn’t raise the bb by 20mm but should do at least for the 7mm lost with the change in tires/wheels.
 

mtbiker87

Well-Known Member
Yeah..it will. I can tell the difference since going 27.5 + on the Gnarzan, especially once you figure out that the optimal tire pressure is between 10 and 13 pounds, ( at least for me ) which drops the BB even more. Now, it's more like riding my Chilly with the shock in the low position. Definitely more pedal strike potential than riding with the 29'er set up.
 

Santapez

Well-Known Member
Team MTBNJ Halter's
What size fork are you putting on?

Can you put in an 10-20mm longer air-shaft?

Since I run a lefty on my El Mariachi I increased the axle-to-crown from 490 to 510mm. Put the bottom bracket in a good spot, much better bike for downhill riding with a more slack fork & longer travel. 29" tires.
 

serviceguy

Well-Known Member
What size fork are you putting on?

Can you put in an 10-20mm longer air-shaft?

Since I run a lefty on my El Mariachi I increased the axle-to-crown from 490 to 510mm. Put the bottom bracket in a good spot, much better bike for downhill riding with a more slack fork & longer travel. 29" tires.
Rigid fork for now, which is why I am considering the 20mm offset lower headset cup. I really love this bike, I may convert to a 120mm fork if I can’t find the fabled ruby red geared frame that dreams are made of...
BED8EA49-C6A5-4CD0-92E2-FD6F383ABBDD.jpeg
 

serviceguy

Well-Known Member
Had a quick lap on the 27.5+ El Mar on easy fire roads/trail between Ryerson and Shepherd's pond. Granted I stayed away from technical terrain, but no pedal strikes happened. The type of riding I would be doing with this bike as it is any way so everything is good.
 
Top Bottom