Bike Purchase, Geometry problems


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    • #79401

      Greetings all! Im 30 years old and just purchased my first bike. It’s been a good 15 years since i last got on a bike. Here is my delima;

      Im about 5’6 chubby / fat (kind of a thick build). After doing some research I went to a local bike store (bikenhike) and purchased a Giant Rincon (small). My immidiate concern was crotch clearance on the top bar. From what i understand you are supposed to have 2+ inches of clearance. I had basically no clearance.

      I returned to bikenhike and tested a couple bikes, all of which were small. I had the exact same issue on ALL the bikes. I really liked the Giant Rincon so i exchanged the bike for an extra small ( they had to transfer it from diff. store).

      The XS is intended for hight of approx 5’2 – 5’4. The top bar issue was no longer a problem but now i fell a little scrunched in horizontally! If i stand up on the bike and return to a natural seating positiona i feel like im hanging about 1/3 (or more) off the back of the seat!

      So here i am feeling like im stuck between either slight scrunching horizontally, selecting a womans frame or ZERO clearance on the top bar.

      Is there a resolution to this problem that im overlooking? Maybe seat that is slighty offset to the back?

    • #79402

      Sounds like maybe you have shorter legs with a longer torso and arms than most people your height.

      Here’s the thing…if it comes down to deciding between having a little extra crotch space when I am OFF the bike and standing vs having the correct amount of reach while I am ON the bike and riding, I’d go with reach everytime. You buy the bike to ride it, not stand over it, right?

      Before you exchange your current XS, see if your LBS will fit it with a longer stem, move the saddle aft on the rails (backwards), and maybe even let you try a setback seatpost to see if it makes you feel more comfortable. All of these should give you a little more cockpit space. But, too many changes and you have basically changed the intended geometry of your bike which will also change the way it behaves on the trails.

      The bike shop should have done a body fitting for you when you purchased the bike and that should have given them an idea of which frame you would need. Honestly, if you can touch the ground flat footed with both legs, you have plenty of crotch room to get the job done.

    • #79403

      I have a similar problem. I’m 5’11’ and 195lbs. My inseam is 30" and my torso appears to be longer than most others my height. Most shops put me on a 18"-19.5" frame but I’ve always felt crunched in the cockpit when riding a bike that size. Recently I purchased a XL (21.5") Felt Virtue 2. The guys at the shop figured it was too big, but I feel very comfortable while riding and have never felt crunched. My seat post is still raised up quite a bit. I don’t know if too large of frame changes much of anything but I did the math and geometry calcs and found the frame is only an inch at max larger than the next smaller frame. I figured motorcycles are "one size fits all" so you learn to ride what’s between your legs.

    • #79404

      Welcome KOmen…

      Well I just read your post and I would have to agree with those shops you had visited. I too would do the same for the frame size however from there then you can play around a bit and for example increase the stem length and get you a set back seat post that would take care of your longer torso while keeping your seat tube/ top tube lengths correct..Otherwise you can’t stand over the bike comfortably and perhaps (( not wishing it to happen of course)) hurt the boys down their.

    • #79405

      Ooops didn’t go all the way to the top of the post..The same goes with Mike..There is another thing that sometimes is over looked that can also give another 5mm without throwing off balance however some shops won’t do it simply because they may not have a spare hanging around..Sometimes when I fit people I also play with crankarm length usually you have three choices 170, 175 180mm..Depeneding on brand and quality..For those people otherwise what was mentioned already as to getting a set back post or slightly longer stem or even a riser bar all will help..Just remember the changes are within reason….For example if there was already a 100mm stem don’t be throwing on a 130mm it will really effect the way the bike rides…The most important thing however is the initial fit before purchasing..I always have people test ride the bike first as is. Then a few changes for comfort. Then test another bike…Different manufactures have slightly different lengths and curves that accomidate one body or another…Sometimes frames have a steeper curved top tube that will accomidate those who have slightly short legs than others..Maybe that is something to consider next bike seeing that you already have one otherwise as mentioned before find a set back seat post and maybe a stem +10 – +15mm longer or a riser bar.

    • #79406

      Thanks for the information on the crank length. That’s one of those options no one mentions or even suggests you try. I shortened my stem by 10mm at the shop (came with 120mm and it changed to 110mm) and slid my seat forward, but I have since pushed my seat back for comfort. My seat post is still quite high. I scared the boys only once since riding this bike. I guess one’s riding style should be considered. I enjoy riding intermediate terrain, I only attempt stuff I’m comfortable with (I’m 53, I had my hay day when the bones would heal) and I will dismount when in doubt.

    • #79407

      I’m in the same situation at 5’8" with a 30", well 29"….OK 28.5" inseam…

      My hardtail was a real nutbuster, especially when I went from the 80mm fork to a 105mm. I was also unable to lower the seat very much for steep downhill.

      When I upgraded to a full suspension this spring, one of my goals was to gain some crotch clearance.

      Most modern full suspension frames have a dropped top tube for this very reason, and the Giant Trance that I settled on is a bit exaggerated in this dept.

      I got a small (16") frame and a 100mm stem, so now my legs can reach the pedals, I have crotch clearance, I have lots of seatpost to work with and my fairly long torso gets to stretch comfortably.

      In your case, I would take the above advice and try a longer stem first, then sliding the saddle back, then the laid pack post as a last resort.

      The issue with the laid back seat post is it ends up putting you too far behind your bottom bracket and it can make uphill pedaling a bit uncomfortable when seated.

      Oh yeah, and I went with 170mm cranks as well…

      Check out my avatar for how it looks next to my svelte physique 😕

    • #79408

      Just reading through this post and I have to ask MikeIP… What kind of shop are you working with??? You should be able to go to Your LBS and they will fit you with all of the appropriate adjustments. They should switch out stems and cranks to make sure you get the fit that you are comfortable with. Even if you are not spending $1000’s on a bike any reputable LBS will bend over backwards to fit you correctly. They know that you will eventually come back and buy more!

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