Fork Discussion / Differences

jh4rt

New member
I did a search or three and couldn't find the information I was looking for. I would really like to understand the differences in the forks... and what the deal is with my bikes.

Background. I purchased a M Yo new in 92. It came with a Mag-21. The fork eventually died and I decided to order a rigid fork from Wendyll / Chris.. This was probably in about 97/98. I waited and waited, got what I think is a BOI, installed it and have been riding it ever since.

Skip forward to yesterday. I just purchased a 99 YO on eBay... got it re-assembled it and took it for a test ride before I tear it down and make it SS. WOW !!!!!!! What a difference. The new one has an IF fork on it with a bit more rake, and it is about 1.25" longer than the one on my other. It is so much more stable. My old bike feels like a crit bike now... twitchy as hell. And I feel like I'm a bit dumped. I'm starting to think that Wendyll sent me the wrong length fork for my old yo.

So: Background finished, these are the questions I hope you could help me answer:

1. What is the difference between BOI and Yo fork?
2. How do I measure my 93 to decide if it is suspension corrected?

Thank you in advance
 

colker

New member
I am not sure... That is the fork, right? The fork is a bout 1.25" longer axle to crown... but is the head-tube the right angle, etc???

did you measure the wheelbase on both bikes? susp corrected geometry is always something vague since some forks sag and others don't.
 

jh4rt

New member
did you measure the wheelbase on both bikes? susp corrected geometry is always something vague since some forks sag and others don't.

I didn't measure wheelbase, but all things being equal, if the geometry is the same on both bikes then the new one will have a longer wheelbase. The IF fork is longer and appears to have a slight bit more rake. My other... well... it is so rigid. I mean.. every single bump is transmitted through my BOI/Yo. This IF fork makes a world of difference. I'm kind of in love with it...

Final question. If I was thinking about retiring my BOI for a while and runnning a suspension fork, what would be a good suggestion? I'm not looking for a huge amount of travel; and would want it to be light... and .. of course... it has to have a 1" steerer.

Thanks...
 

colker

New member
I didn't measure wheelbase, but all things being equal, if the geometry is the same on both bikes then the new one will have a longer wheelbase. The IF fork is longer and appears to have a slight bit more rake. My other... well... it is so rigid. I mean.. every single bump is transmitted through my BOI/Yo. This IF fork makes a world of difference. I'm kind of in love with it...

Final question. If I was thinking about retiring my BOI for a while and runnning a suspension fork, what would be a good suggestion? I'm not looking for a huge amount of travel; and would want it to be light... and .. of course... it has to have a 1" steerer.

Thanks...

not necessarily a longer wheelbase. if it was susp corrected it could have a steeper headangle to compensate. susp. forks always had short rakes... but so did the BOI.
 

jh4rt

New member
Pics for side by side comparison

I know ... parallax/angle/ light can play tricks... but side by side, maybe someone can tell a difference?

91 yo / BOI
IMG_1759.JPG


99 yo / IF

IMG_1834.JPG
 
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colker

New member
the newer bike seems to have a steeper head angle which would compensate for the extended A/C and modified rake.
rake/ head angle/ front center distance all play together. hard to pinpoint what exactly goes there but if you are in love w/ the new one.. does that mean we will be seeing a black Yo eddy for sale soon?;)

I know ... parallax/angle/ light can play tricks... but side by side, maybe someone can tell a difference?

91 yo / BOI


99 yo / IF

 

colker

New member
NFW!!!!

But, I do think I would like to put some small suspension fork on my old yo / gearey... But this ol' yo is never leaving my stable.

;-)

look for a 1in marz bomber on ebay. or a 11/8 in nice shape and buy just a steerer. i wouldn't use anything else on a bike as a yo, made for attacking steep technical terrain. don't go w/ flexy sids, judys etc..
70mm travel is the ticket.
 

rody

New member
Hey guy,

Here are the major differences in the forks / frames...




Big One Inch specs...

Debut around the time of the TI introduction

Dropout to race length - 15.9375" suspension corrected to 63mm


Rake offset - 1.57" or 6 degrees


BOI forks use 1.0" diameter tubing for the legs and crown

Yo specs...

Used from late eighties until BOI intro

Dropout to race length - 15.5" for standard geometry

Yo Eddy forks use 1.125" diameter tubing for the legs and crown.

Now, the frames will have a significant difference in the geometry.

Your 92 Yo will have a lower headtube height as it was designed for rigid forks, although the Mag 21 was probably put on as with your weight to sag the fork, it would not change the ride drastically.


Your 99 frame is designed to work with a 80mm fork, thus the reason that the longer axel to crown length is present on the IF fork.

The likely culprit of the handling variance of the older Yo is the resultant trail with the more modern Big One Inch. Only way to tell for sure is to take all the measurements off the rigid fork that is on it.

Hope some of this helps,

rody
 
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jh4rt

New member
Thanks Rody.

Awesome information....

Well... So... umm... I took the old nag out for a 15 mi. spin this evening. Let me just say... umm... crit bike; whatever... IT RODE LIKE A DREAM. Maybe my kung fu is just getting stronger, but it was a dream to ride tonight. And, I realized that both of these bikes are stellar, but different. The IF fork is much more flexy, and I think will be better suited for a SS. But my old Yo with the BOI was true as can be tonight. I have actually changed the stem and bars and am now running a 100mm Salsa stem with Syncros riser bars. CLASSIC and much more comfortable, cooler.

Thank you everyone for the information. I think I'm going to stick with this ol' BOI on my geary.

--j
 

lucifer

New member
Fast handling was kind of the norm for east coast bikes back in the day. Your real problem is that you live in california and you are riding the bike on trails that are way too smooth and wide... :)
 

jh4rt

New member
Fast handling was kind of the norm for east coast bikes back in the day. Your real problem is that you live in california and you are riding the bike on trails that are way too smooth and wide... :)

HeHe. You obviously haven't done Guadalasco to the Backbone. I was scraping bush on one side and rock on the other last night. ;-)

--jim
 

bushpig

New member
rody - do you know what size canti studs I need for a BOI fork? I have seen different sizes of threaded studs and want to buy the right size.

Hey guy,

Here are the major differences in the forks / frames...




Big One Inch specs...

Debut around the time of the TI introduction

Dropout to race length - 15.9375" suspension corrected to 63mm


Rake offset - 1.57" or 6 degrees


BOI forks use 1.0" diameter tubing for the legs and crown

Yo specs...

Used from late eighties until BOI intro

Dropout to race length - 15.5" for standard geometry

Yo Eddy forks use 1.125" diameter tubing for the legs and crown.

Now, the frames will have a significant difference in the geometry.

Your 92 Yo will have a lower headtube height as it was designed for rigid forks, although the Mag 21 was probably put on as with your weight to sag the fork, it would not change the ride drastically.


Your 99 frame is designed to work with a 80mm fork, thus the reason that the longer axel to crown length is present on the IF fork.

The likely culprit of the handling variance of the older Yo is the resultant trail with the more modern Big One Inch. Only way to tell for sure is to take all the measurements off the rigid fork that is on it.

Hope some of this helps,

rody
 

rody

New member
Noah,

I'm out of the shop until Monday...I'll take a look at the post id and let you know.

rody
 

RobTu

New member
Hey guy,

Here are the major differences in the forks / frames...




Big One Inch specs...

Debut around the time of the TI introduction

Dropout to race length - 15.9375" suspension corrected to 63mm


Rake offset - 1.57" or 6 degrees


BOI forks use 1.0" diameter tubing for the legs and crown

Yo specs...

Used from late eighties until BOI intro

Dropout to race length - 15.5" for standard geometry

Yo Eddy forks use 1.125" diameter tubing for the legs and crown.

Now, the frames will have a significant difference in the geometry.

Your 92 Yo will have a lower headtube height as it was designed for rigid forks, although the Mag 21 was probably put on as with your weight to sag the fork, it would not change the ride drastically.


Your 99 frame is designed to work with a 80mm fork, thus the reason that the longer axel to crown length is present on the IF fork.

The likely culprit of the handling variance of the older Yo is the resultant trail with the more modern Big One Inch. Only way to tell for sure is to take all the measurements off the rigid fork that is on it.

Hope some of this helps,

rody

Great info; thanks.
 

Upchuck

New member
Fast handling was kind of the norm for east coast bikes back in the day. Your real problem is that you live in california and you are riding the bike on trails that are way too smooth and wide... :)
You're thinking NorCal. We live in SoCal: the land of rocks and cacti. We have plenty of high pucker-factor riding out here. ;)
 
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