[drm31078]

I just bought a 2008 Fuel EX 8 and it is a size 19.5". I am having some lower back pain when I ride 3-4 miles. I'll be the first to admit that I don't maintain great posture, but I was wondering if maybe the bike size can be tweaked to help me out. The LBS suggested maybe going from the 7 deg. stem to the 17 deg. stem? Or maybe a shorter stem? Hopefully I didn't get the wrong size bike?!?! Here are my dimensions based on http://www.competitivecyclist.com:

Inseam: 34.25"
Trunk: 27.75"
Forearm: 14"
Arm: 25.5"
Thigh: 24.5"
Lower Leg: 24.75"
Sternal Notch: 59.75"
Total Body Height: 72" (6 ft)

Any recommendations?

 

[sponger]

I also have back problems and I do feel some improvement when I'm able to sit more upright on my bike.

That's why I keep my seat lower than what is probably considered "optimal." Also, I did shorten the stem, and that helped somewhat.

Being that you have long legs, it's probably more awkward for you to lower the seat than it is for me. My inseam is like 29.5", so I have fairly short legs for someone who is 5'10".

 

[eddie_e46]

I know exactly what you mean. Between golf and this....my back is killing me and I'm in the 30's. Anyhow, I bought the Bonty X lite 17 degree/75 mm. I've only been on the bike with the new stem a couple of times and so far I can tell the difference - a bit more upright. The only thing with it being 75 mm, since I'm 6'1", I had to pretty much move my saddle all the way back - which is no big deal. However, one good thing with it being 75 mm, the bike handles a bit better.

 

[Blk02]

Back pain could be caused by a incorrectly sized frame. I am 6'-2" with a 33" inseam and ride the extra large EX8. I could tell that my lower back would arch slightly when riding the large. I have this same issue when I ride my old 20" GT hardtail. My back will be in pain after a fairly short ride. Really nothing substitutes for a proper fitting frame. I fought with my LBS about the proper fitting bike. I thought the large was my ticket for the longest time. I had one of the specialized trained fit experts watch me ride and he had no doubts about putting me on an extra large. I came to the same conclusion after riding the large and x-large back to back several times. The difference is very slight and takes time to notice. If you are used to riding an under sized frame you tend to think the smaller frame is better. I am very technical in nature and I tried all the bike fit caluculators. I came to the conclusion that none of them really tell you exactly what you need. The only way to truely tell what works is to ride it for atleast 30 minutes and try all sorts of positions and try to take it off the road. In addition, have someone watch you that knows how to size a bike. 90% of bike stores have no idea how to properly size a bike.

At 6ft with a 34.25" inseam I would say you are close to stepping up to the next size. With your inseam the seat is probably not at the optimum height on a 19.5" frame. The seat is most likely too high if you are striving for the optimal pedal distance. Then you need to take into consideration the reach on an xlarge. Generally back pain is attributed to being to tight in the cockpit. Your lower back (pelvic region) becomes arched because you are trying to keep your butt on the seat. This is not a relaxed state therefore your body must strain to stay in this position during your entire ride. This strain leads to a sore back. The bend in your lower back is very slight and hard to notice.

I am by no means an expert but I have been researching bike fit for several years now trying to figure out my own situation before I drop $2400.00 on a new bike. Like I said I am very technical and enjoy researching topics.

General Sizing Guide from Trek's Website:

Height
Mountain

<5’2”
13/14

5’3”
13/15

5’6”
16/18

5’9”
18/19

5’11”
19.5/21

6’2”
21/22

6’3”
22/25

6’4”
25

 

[Blk02]

Another thing that LBS's try to do is steer you away from buying a size that they do not stock. If all they have are larges then some of them will try to sell you a large even though you may be an extra large. This can also happen in reverse. If they have extra large bikes they might try and push them on you because they do not turnover like the medium sized bikes. Keep in mind that your LBS is a business trying to make money and they want a quick turnover on their inventory. You must do your research to find a neutral LBS that will tell it to you straight. Ask them about what store to go to for a high end brand that they do not carry. If they try to steer you away from that store or brand try another LBS because they are trying to sell you on what they have instead of helping the customer. A good LBS will recommend other good stores to test other brands they do not carry. The tech or salesman in a good LBS will also be knowledgeable about other brands besides they ones the shop carries.

 

[senseamp]

Sizing seems right. I am about your size and ride a 19.5 too. I actually have fairly short arms, and on my road bike use a short stem, but the Fuel EX8 stem seems fine to me.
There is some sizing discussion here on Trek's blog:
http://trekmountain.typepad.com/king/2007/08/2008-fuel-ex-ge.html
Maybe you should start with the seat, moving it on its rails, then pick a stem.
You want your front knee directly above the pedal axle when your pedals are in 3:00 position. Then find a stem that is comfortable for you with seat in that position. Or go to a store and ask them to fit you properly.

 

[shmooove]

Do you feel like you are stretching to reach the handlebars or are you crunched up in the cockpit? Sitting more upright definitely helps me when I am riding so I tend to use my bar ends when I am just cruising. That may help you a bit as well with a change in stem angle.

I know it can be tough but proper posture is a must for every activity. (I need to follow my own advice more, especially at work!) I would highly suggest working at that.

While I have not experienced any major physical problems with my 18.5" EX8, I have noticed a slight tightening in my lower back and a little more neck stiffness than with my old K2 hardtail. My 2 hour ride Sunday left me feeling pretty good (mainly tired ) but as I mentioned, with just a slight tightness in my lower back and neck. I will have to see how I feel as time goes on but I am initially attributing this to an increase in ride time and adjusting to a new bike. Plus shaking off the winter, desk-job cobwebs.

Even though we are about the same dimensions, I personally went with the 18.5" frame instead of the 19.5" because it felt like I was stretching on the larger one (which now I think could have been adjusted with a shorter stem). But even with the results from www.competitivecyclist.com, the recommended Tube Top Length for me is 24.1 - 24.5 and the 18.5" EX8 comes in at 24" while the 19.5" is 24.7". So I obviously went smaller, which I hope does not turn out to be a mistake.

In case you were wondering, here are my rough measurements from the same site:

Inseam 34.25 in
Trunk 25.375 in
Forearm 14 in
Arm 27 in
Thigh 24.625 in
Lower Leg 23.25 in
Sternal Notch 58.5 in
Total Body Height 71 in

 

[drm31078]

Thanks for all the posts...I am on my 4th ride with this bike and things seem to be getting better as I tweak seat height/position. I went today and really focused on my riding position. Afterwards the back seemed okay. I think my seat is a little low for optimal performance so I am considering getting the 17 deg stem to help me out. Not sure if it will change the performance of the bike at all? Or is is recommended to get a shorter stem instead?

The LBS is willing to work with me and I feel like the bike is the right size the more I ride it. Although I do have a long inseam, I feel like my torso is short (relatively speaking). The LBS suggested riding it for 2 weeks and then coming back and tell them my issues to figure out what to do. So I might head back there next week.

As for fore-aft position, the knee should be over the pedal axle, however it is really the muscle/bone just under the knee cap that should be over the pedal axle, correct? I am a number cruncher myself so I like to be as precise as possible. I tried to plumb bob it myself but it is kind of tough. Also, do you set the seat height first and then the fore-aft position?

 

[Guest]

Jeez, I just wrote a friggin' novel here and my PC crashed before it posted. Anyway, check this out:

http://www.sheldonbrown.com/kops.html

Bottom line: KOPS is over-rated. Stimulate the economy by buying some stems and seatposts with varying setbacks. Experiment. You know you are close, just fine tune it.

 

[Guest]

PS: Trek chart cited above is way off base. Do the math. Trek doesn't make a 25. Or a 24, 23, or 22. In fact, their largest actual is a 20. What are you big guys supposed to ride? It also says I should ride a 16/18, which, if I did, I could sing in a choir if you know what I mean. I like a little "breathing room" thank you. Just experiment. It is very unlikely that any bike will fit perfectly right off the showroom floor.