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Seeking Grom fork dimensions

42K views 36 replies 10 participants last post by  fatcaaat 
#1 ·
Can someone out here on the board please give me some dimensions of the Grom forks?

1. Clamping diameter at top
2. Clamping diameter at bottom
3. Total length from top to axle center
4. Axle diameter

Info is greatly appreciated...thanks.
 
#13 ·
Chad...another question if you dont' mind. What is the offset of a standard fork setup? Also what are the dimensions of the inner to inner at the axle and inner to inner where the fork uppers and lowers come together at the tightest? A standard set of grom trees could potentiall work.
 
#15 · (Edited)
There's a couple of potential issues which is why I 'm doing all this research. First, the Grom forks do not look like they have much offset. Standard monkey/ct70 have 40mm and you can buy trees that have 55-60 which slightly extends the wheelbase and moves the tire forward so your bigger engines can clear. Another issue is height. Standard height of zokes is 730mm and not even sure if you can get 650mm anymore. That is way too long for a grom. A standard ct70 fork is 610mm.

Reports of grom forks being too soft are all over, meaning you need to upgrade 300 bucks to make them work well. However, KSR110 forks are available and they are awesome with just adding 10wt oil and preload adjusters in 650mm. Still cost 600 bucks though
 
#23 ·
Thanks again. I think i have all I need at this point but it's hard to tell in one of the pictures what the measurement is...it is the first one...i can't tell where I should look on the tape. That one is the center to center of the forks measurement right? I suppose you can take that from anywhere...tree, forks in the middle, or even at the bottom..the important thing is that it is center line of the forks to ccenter line of fork...and based on angle, it looks somewhere between 7 and 7.5 inches.

To effectively work on a ct that measurement will need to be over 7" and under 7.5...which could be...can you confirm...no picture needed...just the number...picture if you have the notion...
 
#24 · (Edited)
Be sure to keep in mind the axle location on the fork bottoms. The Groms are on fork centerline, while the Zokes/Fast Ace are forward of the axle. This needs to come into play when planning your custom triple offset. If you install a set of Zokes on the standard Grom triple offset, it will shorten your trail (by moving the axle forward) and has the potential to make the bike more sensitive to bar input (twitchy). To have the same trail as stock, you will have to make the offset of the triples shorter the same distance that the Zoke axle location sits off of centerline. This may also cause contact issues of the forks with the tank or frame at full lock.

I can see why the Grom has the axle on centerline of the forks. If they are using triple/steering head geometry similar to my X4, they did this to make it more stable at speed. My X4 was twitchy on the freeway in stock form.

Also, not sure if Fast Ace stopped selling the 650mm forks. I purchased a set last Fall with no problems.

I am also interested if someone could measure the steering head angle on the Grom.
 
#27 ·
A quick measurement in the garage looks like it will have the Zoke forks at 20cm on center to fit the Grom front wheel and spacers. That will leave a little over 14.5cm between the insides of the fork seal area for tire clearance.
I'm going to try and get into work next week and start drawing things up.


Any suggestions on offset changes for street use versus standard offset for dirt on the KLX?
 
#29 ·
I am also putting grom forks on a ct70. The problem I ran into is the CT stem is longer.If you use the Grom lower triple with a CT stem the top clamp will not reach down to the top of the forks. Also the ride height is about 3 or four inches too tall. FYI the Grom forks centerline dimension is 204 mm.
 
#31 ·
Well, we all knew that the stem was going to be too short, so that needs to be swapped. For the height, it might work out actually. The stock grom forks are way too soft. So, you can effectively shorten the grom forks and retain or slightly trim the stock springs and you should be in business. Problem is I don't know how far you can shorten the legs until they bottom out.

I ended up using a set of ksr110 forks on one bike and a set of fastace forks on another. On both, I ended up sliding the forks up in the tree about 1/2" and then also adding 1" to the rear shocks. Work great!
 
#37 ·
I did complete this swap as well a while back. A direct swap and shuffling the forks up as far as possible and it choppers the bike by about 1-1.5" You can correct that by running 345-350mm shocks out back or if you can make custom trees to change the clamping positioning.
 
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