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Kargaburun5

Spring Dimensions of Bitubo JBH12 Cartridge Kit

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2 months ago i ordered Bitubo JBH12 cartridge from omniaracing for a 70/80 kg rider for street use only. When installing kit i compressed the spring and i was dissapointed to see 0.90 (or 9.0 i don't remeber) etched on it.

 

My sag values are much lower than Bitubo recommends on its manual. Static sag is about 19 mm and free sag is no higher than 25 mm with zero preload and compression leg fully open (20 click ccw). I am 78 kg in full gear. Although omniaracing insisted "don't worry, you receive with correct load" i contacted Bitubo and their tech department suggested their 0.80 kg/mm MX65 spring kit "if i find the ride uncomfortable".

 

I read about@etorty's situation and he seems to be content with his K=0.80 springs.

 

My questions are:

 

1- I couldn't find MX65 kit on online stores and since I don't have or couldn't find spring dimensions of Bitubo, can i use other brands? Is Öhlins's spring kit for NIX22 or K-Tech's IDS20 spring kit equivalent to Bitubo JBH12 cartridge kit?

 

2- At Yamaha website 0.90 kg/mm spring rate is recommended for NIX22 kit for 70-89 kg riders. What may be the reason behind this? Track use?

 

3- I know this is subjective but is K=9 spring usable for my weight on street? It is really dissappointing having to buy another set of springs for a brand new cartridge kit that you have already paid for.

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1) let me go measure my bitubo springs and also how much preload is built-in.

2) yes, track use. 0.9 can potentially work for you if you take a lot of the preload out of the system.

3) I would have suggested 0.85kg/mm or 8.3N/mm

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I disassembled the forks. Spring length is 245 mm. There is an additional 5 mm spacer on top of it. So 250 mm spring is also a drop-in replacement.

ID is 25.5 mm and OD is 34.5 mm.

 

I ordered K-Tech 36-260-80 fork spring which is 260 mm long and has an OD of 36 mm. With a probable thickness of 10 mm it should be compatible with Bitubos.

Edited by Kargaburun5

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