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err, 27.5+
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Discussion Starter · #1 ·
So I finally got around to checking my initial geometry numbers on my Semi-custom X5. I swapped out the fork, so some investigation into setup was called for.

Setup:
21" X5, 5/6-rockers, 2007 Talas 36 100-160mm fork
Measurements taken with bike on a flat 2x4 with a SPI digital protractor (give or take .1*)

Here are the results:
5" rear / 130mm front : 68.3* HA
5" rear / 160mm front : 67.3* HA
6" rear / 130mm front : 69.3* HA
6" rear / 160mm front : 68.3* HA

Pretty much standard fare. 25-30mm travel change at either end works out to about 1*.

Other points of interest are in sag measurements. I am about 235-240lb depending on geared up vs. street clothing. My DHX coil has a 600lb spring.

In the 5" rear mode 1-turn of preload on the coil equates to approximately 2% difference in sag.

In the 6" rear mode 1-turn of preload on the coil equates to approximately 3% difference in sag

One last item that I noticed:
Despite the talas being a linear fork it's sag values change inversely to that of the rear suspension. I would imagine this has something to do with the weight transfer and unweighting of the front end as the rear sags more.

Example:
5" rear, 130mm front
2-t preload rear, 100psi in fork
sag balanced at about 23% front/rear

Compare to:
6" rear, 160mm front
3-t preload rear, 100psi in fork
sag rear:28%
sag front:20%
Kind of a weird balance on paper, but it rides well. It can take big hits and rides tall in the front. Good for more aggressive riding. I am going to have to play with the damping to see if there is any negative effect on small bump performance with this little sag.
 

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I'll bite on this topic...

This is very close to my setup and weight. How much sag do you end up with using the 600lb spring? I didn't go much past the 2 turns as the manual said not to exceed that. However, I think I don't have enough preload, i.e. sags too much.

How do you like the 36 talas? I was thinking about that one as it seems to be perfect in 5 or 6 inch mode, but I opted for the well received pike 454 uturn instead. Overall, my bike is plush and stable, but seems a tad slow to pedal....

Does your front end feel light, especiall uphill, with 160mm travel up front?
 

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err, 27.5+
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Discussion Starter · #3 ·
OTE, preload is limited with this setup. It also varies from coil to coil (ie 2.3 vs 2.35 coil). But I think 2-3 turns is usually okay.

The talas is still under initial evaluation. I think this fork would really suck for someone that doesn't want to invest time into finding the correct setup. After a couple of weeks I am still playing around with different pressures and damping. I don't really support linear forks much, but this is a case where it was down to this or a 66 SL and the SL just looked like it would be too much fork for this bike. Since I wanted a fork that would work well for both 5 and 6 inch rear travel it made sense to give it a try. I am actually impressed with it so far. I do have a couple of nit pic's, but I will air those out later. The talas 36 actually bobs less than the pike 454 air it replaced despite me having the talas setup much softer.

The front is a bit light, basically when I am climbing most of the weight shifts over the rear which makes the sag imbalance even worse. I find that I usually drop the front to the next lowest talas setting when the climbs are steep or longer than a minute or so. I could run lower pressure in the fork, but then it would be too soft in the 5in mode. I dunno. Like I said, still a work in progress. I just wanted to throw out some numbers because I mentioned that I would in the thread I had running on the 66 SL ata.
 

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dscot420 said:
but this is a case where it was down to this or a 66 SL and the SL just looked like it would be too much fork for this bike. Since I wanted a fork that would work well for both 5 and 6 inch rear travel it made sense to give it a try.
That was exactly my dilema when choosing a fork for my x5 with 5/6 rockers. The 66SL seems like a great fork, but seemed way too much in 5" mode. Probably OK if you're using the bike exclusively in 6" mode. Since I had used a 32 Talas for a while, I thought I'd give the pike a try, even though the 36 talas seems to cover 5" and 6" modes better. It didn't hurt that so many people love the pike and I got a smoking deal on it. However, at times it seems under sprung for my weight. Do you know if going over 170 psi in + chamber is really bad for it?
 

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err, 27.5+
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Discussion Starter · #5 ·
Honestly I haven't had to pump it higher than 170. I don't think it would hurt anything to exceed it by 5-7psi, but if you are simillar weight to me I would imagine that would result in a fairly stiff ride.
 

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Basura Blanca
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Same thoughts on sag

FWIW, your sag numbers aren't jiving with my experience. I weigh 200#, so maybe add another 20# for gear, etc. and I'm still way lighter than you two. I've got an '04 X-5, running a 150mm fork. When I bumped up to 6" rockers, giving me 5.3" travel with the original Romic, I had to move up from a 600 to a 650 spring to keep the sag at ~25 to 30%. With the 600 and 3 turns of preload (max recommended, IIRC), it was sagging way more than 33%. Not calling BS, just observing the difference in experiences. Wierd. Thanks for posting up the info! BTW, how were you measuring sag? Shiggy posted a pretty cool sag gauge a while back made from a CD and a spoke, but I haven't taken the time to fab one up on my ride.
- Joe
 

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err, 27.5+
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Discussion Starter · #7 ·
I use an 8" digital caliper to measure sag. I zero it to the spring length. Sit on the bike and remeasure, which gives the amount I have compressed the spring. I can then take this number as a ratio with the full stroke to come out with the percentages. I use the measure twice and average the result to make sure I don't have any gross miss-read on measurements. I don't claim these to be the Gospel, just what I measured. There is always room for error in sag measurement unless a dedicated fixture is used or multiple people help ;)

I do get more sag in the 6" mode for sure due to leverage. I just generally feel that in the longer travel mode that I want the bike more dh oriented, so I am okay with 28-30% sag. If I were going to have it dedicated to 6" with a full time 6" fork I would shoot for 23-25% sag to make pedalling a bit better. Oddly enough I actually think that the rear suspension likes more sag. When it is closer to 30% sag it actually has less pedal induced bob than at 20% sag. I don't know if this is in design or just me not noticing bob as mush while farther into the travel.
 

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err, 27.5+
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Discussion Starter · #8 ·
Okay, I am going to take back the comment about the 66 being too long for the X6. I have been hitting some sketchy steeps in the last week and running with the 5" rear travel and 160mm up front is actually a blessing. So having a fork that is an extra inch longer than 6" would be beneficial if you planned on running the rear of the bike at 6in for general trail riding. Then on really steep, pucker type, dh the 66sl could be let out to the full "175mm" of actual travel and give some more descending confidence. Maybe this is what all those Homers are up to.
 

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I've put my 66SL and Coil Vanilla on my X5 for the next few rides.

Unfortunately, poorly kids, work and the windy British weather are all conspiring against me this week.:madman:

Hope to have a few comments about it for general trail work rather than uplift orientated days, where I would just pick a travel (160mm) and leave it set at that.

As you mention dscot420 i'll have to get my shock pump out and start to adjust the travel to see what best suits:confused: . One shortfall with the 06 66SL.
 
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