Need help!! Just picked up a Trek 7.5fx, not happy-it has a problem with front der...
#1
Member
Thread Starter
Join Date: Apr 2011
Posts: 33
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Need help!! Just picked up a Trek 7.5fx, not happy-it has a problem with front der...
I picked up a Trek fx 7.5 the other day, it seemed as if there was a derailer adjustment issue. I noticed that when I was in the middle ring in front, the rear 4 largest gears caused a rubbing noise on the derailer in front. The strange part is that I always thought that bikes would sometimes make some noise if you were on the extreme cross chain situations, on my bike those situations seemed ok though. I brought it back to the shop and it seemed like the mechanic was struggling to get it quiet. He mentioned that the new 2011 design on the deore derailer had tighter tolerances. The strange part is that my brother got the same bike on the same day, built by the same mechanic, and has no issues! The mechanic finally got it to work normally, but it seems that the adjustment is still a little off and drifts. I looked a little more carefully today, and it seems like the front gears have a little runout in them, maybe the thickness of 2 dimes. I have a feeling that this is what is eating up his tight tolerances and causing the rubbing. Is it normal for the gears to have a little runout in them? Shouldnt they spin perfectly straight? Did any of you ever hear of anything like this? I'm really upset, I was looking forward to this bike so much, now I feel like I made a bad decision. I'm taking it back again tomorrow, is there anything I can suggest or request from them? Any suggestions on what it might be? Thanks.
Chris
Chris
#2
Constant tinkerer
Did you just buy it brand new? The FD should not rub, except maybe when in the extreme combinations. It should definitely not rub in four of the gears. Take it back, tell them they need to fix it.
If the chainrings are actually bent as you describe, they could be defective and need replacing.
If the chainrings are actually bent as you describe, they could be defective and need replacing.
#3
Member
Thread Starter
Join Date: Apr 2011
Posts: 33
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Jake, it's a brand new bike with about 15 miles now. That's why I'm so upset about this. My daughter has a $230 diamondback with much lower end components, and hers shifts perfectly, my wife has a $350 Univega, also with lower components that also shifts perfectly. I also, unfortunately, just sold my 13 year old Raleigh M-80 that was in showroom condition, never had a problem. Now that I spent close to $1,000 for a bike I'm having all kinds of problems. I definitely expected much better out of this bike, and to say the least, I'm disappointed. Thanks for your input, I think I'll point out the chainring situation tomorrow, maybe the mechanic never saw the problem. Or maybe they tried to avoid changing parts by "adjusting" the problem away.
#4
Senior Member
Join Date: Aug 2010
Location: Washington
Posts: 472
Bikes: Serotta Davis Phinney, 1992 Serotta T Max,1984 Specialized Allez, Olmo, 1974 Strawberry,Redline bmx, ect.,
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
It could also be a mechanic that is unsure of the adjustments needed to fix the problem. He is correct about the front deraileur has been changed and is a lot more sensitive to rubbing both inner and outer cage plates if not set up right. The cranks need to be torqued to about 30 ft. lbs. possibly loose from reassembly or from factory. F/derailur should be parallel to chain rings and with the chain in small ring in back and midde ring front the chain should just barely clear the outer cage plate of the front deraileur. Then adjust cable tension to get this to happen. Next check inner ring adjustment as well in the same rear cog, and can probably tighten up this adjustment as well, then back to middle and check cable tentio again. That should get your new ride fixd.if you need more help go to Park tool.com
#5
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,712
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5781 Post(s)
Liked 2,577 Times
in
1,428 Posts
Let's keep it as simple as possible. it's a brand new bike, and the owner is entitled to have a bike that works as intended. If the bike's FD cannot work correctly - by design - than the buyer should have been told that's the way it is.
Actually, I don't think there's any problem, except possibly for sloppy assembly and adjustment. (with the understanding that there is some degree of crossover limitation). The OP doesn't have to go to any site, check crank torque, or FD alignment. That's not his job, it's the job of the shop that sold the bike.
It's very simple, new bikes should be delivered in top working order. Anything less than that is unacceptable.
Actually, I don't think there's any problem, except possibly for sloppy assembly and adjustment. (with the understanding that there is some degree of crossover limitation). The OP doesn't have to go to any site, check crank torque, or FD alignment. That's not his job, it's the job of the shop that sold the bike.
It's very simple, new bikes should be delivered in top working order. Anything less than that is unacceptable.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#6
Member
Thread Starter
Join Date: Apr 2011
Posts: 33
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Thanks for all the info. FBin NY, I agree with what you said, I just bought a new bike and it should be perfect. I think Nwbikeman was just trying to give me different possibilities at this point. I am definitely not going to mess with it at this point. I honestly don't think it is incompetency of the mechanic though. He seemed to have his stuff together. And like I said previously, he assembled and adjusted my brothers (same bike) perfectly. I think there is some kind of malfunction, that's why I was asking if there is a certain amount of "normal" runout on the chain rings.
Thanks again guys, I'll let you know how it pans out after tomorrow.
Thanks again guys, I'll let you know how it pans out after tomorrow.
#7
Senior Member
Join Date: Jul 2010
Location: Victoria, Canada
Posts: 1,541
Bikes: Cannondale t1, Koga-Miyata World Traveller
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 0 Post(s)
Likes: 0
Liked 3 Times
in
3 Posts
My ultegra brifter for a 50/39/30 triple crank clicks 4 times to give me 5 positions.
50 > trim click > shift click > 39 > shift click > trim click > 30
Try clicking your left shifter very gently and listen/feel for the trim clicks. These positions prevent rubbing.
I know your shifters are different than mine, but maybe they work the same.
50 > trim click > shift click > 39 > shift click > trim click > 30
Try clicking your left shifter very gently and listen/feel for the trim clicks. These positions prevent rubbing.
I know your shifters are different than mine, but maybe they work the same.
#8
Senior Member
Join Date: Jun 2007
Location: A Coffin Called Earth. or Toronto, ON
Posts: 12,257
Bikes: Bianchi, Miyata, Dahon, Rossin
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Likes: 0
Liked 5 Times
in
5 Posts
My ultegra brifter for a 50/39/30 triple crank clicks 4 times to give me 5 positions.
50 > trim click > shift click > 39 > shift click > trim click > 30
Try clicking your left shifter very gently and listen/feel for the trim clicks. These positions prevent rubbing.
I know your shifters are different than mine, but maybe they work the same.
50 > trim click > shift click > 39 > shift click > trim click > 30
Try clicking your left shifter very gently and listen/feel for the trim clicks. These positions prevent rubbing.
I know your shifters are different than mine, but maybe they work the same.
most likely case, the FD cable needs to be tightened just a bit.
__________________
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
Food for thought: if you aren't dead by 2050, you and your entire family will be within a few years from starvation. Now that is a cruel gift to leave for your offspring. ;)
https://sanfrancisco.ibtimes.com/arti...ger-photos.htm
#9
Senior Member
Take it back to the shop. Explain your displeasure, try not to get emotional. Suggest that chainring/crank runout may be out of tolerance, especially with the new der design, and that perhaps they could see if Shimano would replace the crank under warranty.
#10
Thrifty Bill
Join Date: Jan 2008
Location: Mountains of Western NC
Posts: 23,525
Bikes: 86 Katakura Silk, 87 Prologue X2, 88 Cimarron LE, 1975 Sekai 4000 Professional, 73 Paramount, plus more
Mentioned: 96 Post(s)
Tagged: 0 Thread(s)
Quoted: 1236 Post(s)
Liked 964 Times
in
628 Posts
Brand new bike? Purchased from a bike shop? Don't be upset, just take it back to the shop.
You pay a hefty premium when you buy a new bike from a shop (versus a used one off C/L or whatever). Part of this premium is having someone to stand behind it. You paid for that service, I would use it.
Once you start tweaking on stuff, if you are unsure what you are doing, you could just make it harder for the bike shop to sort out.
You pay a hefty premium when you buy a new bike from a shop (versus a used one off C/L or whatever). Part of this premium is having someone to stand behind it. You paid for that service, I would use it.
Once you start tweaking on stuff, if you are unsure what you are doing, you could just make it harder for the bike shop to sort out.
#11
Mad bike riding scientist
Join Date: Nov 2004
Location: Denver, CO
Posts: 27,362
Bikes: Some silver ones, a red one, a black and orange one, and a few titanium ones
Mentioned: 152 Post(s)
Tagged: 1 Thread(s)
Quoted: 6219 Post(s)
Liked 4,218 Times
in
2,365 Posts
I picked up a Trek fx 7.5 the other day, it seemed as if there was a derailer adjustment issue. I noticed that when I was in the middle ring in front, the rear 4 largest gears caused a rubbing noise on the derailer in front. The strange part is that I always thought that bikes would sometimes make some noise if you were on the extreme cross chain situations, on my bike those situations seemed ok though. I brought it back to the shop and it seemed like the mechanic was struggling to get it quiet. He mentioned that the new 2011 design on the deore derailer had tighter tolerances. The strange part is that my brother got the same bike on the same day, built by the same mechanic, and has no issues! The mechanic finally got it to work normally, but it seems that the adjustment is still a little off and drifts. I looked a little more carefully today, and it seems like the front gears have a little runout in them, maybe the thickness of 2 dimes. I have a feeling that this is what is eating up his tight tolerances and causing the rubbing. Is it normal for the gears to have a little runout in them? Shouldnt they spin perfectly straight? Did any of you ever hear of anything like this? I'm really upset, I was looking forward to this bike so much, now I feel like I made a bad decision. I'm taking it back again tomorrow, is there anything I can suggest or request from them? Any suggestions on what it might be? Thanks.
Chris
Chris
The chainrings on all of my bikes aren't perfectly straight. Each has a slight wobble to it especially after having ridden them for many miles. It's (almost) normal. A millimeter (thickness of 2 dimes) seems a little excessive. Mention it to the mechanic.
If nothing else, ask, nicely, to have another set of eyes look at the bike. Maybe they'll see something that the first mechanic missed. Be patient and be nice.
__________________
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
Stuart Black
Plan Epsilon Around Lake Michigan in the era of Covid
Old School…When It Wasn’t Ancient bikepacking
Gold Fever Three days of dirt in Colorado
Pokin' around the Poconos A cold ride around Lake Erie
Dinosaurs in Colorado A mountain bike guide to the Purgatory Canyon dinosaur trackway
Solo Without Pie. The search for pie in the Midwest.
Picking the Scablands. Washington and Oregon, 2005. Pie and spiders on the Columbia River!
#12
Senior Member
Join Date: Sep 2004
Location: boston, ma
Posts: 2,896
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Likes: 0
Liked 1 Time
in
1 Post
if the crank arm spider has some run out remove crank and put it on all 4 different position. i think these are square taper cranks. anyways the 7.5fx from trek is a pretty good bike and very easy to adjust. if has the shadow style rear derailleur then b tension adjustment is critical
#13
Member
Thread Starter
Join Date: Apr 2011
Posts: 33
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Thanks for all the responses. I just got back from the shop. It looks like the FD needed a little tweaking again, mostly cable adjustment. It seems like at the cross chained situations at both extremes, I get an intermittant and very slight rubbing. I know that if the chainrings were perfectly straight, this wouldn't happen but the mechanic at shop said that the slight wobble I have is "normal". I looked at other bikes in the shop and they were the same as mine. The weird part is that the one extreme cross chain situation, the chain rubs on the inside of the derailer, and on the other extreme, it seems to rub on the outside. It looks like the FD needs a wider range of movement on the range of motion at the extremes. I have to assume that if this was adjustable, he would have taken care of it. Maybe this bike is different than what I'm used to because the extra gears? I think it is working somewhat normal now, what do you guys think? I am going to put a few hundred miles on it, and get it tuned up after it breaks in for a while. I have to imagine that it can be adjusted more accurately then.
Last edited by up4speed; 04-16-11 at 10:20 AM.
#14
Seńor Member
Join Date: Aug 2006
Location: Long Island, NY
Posts: 353
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Likes: 0
Liked 0 Times
in
0 Posts
Obviously you don't want to crosschain your chainrings and the cassette (biggest-biggest or smallest-smallest). In addition to chain rub, crosschaining will kink the chain and subject the teeth on the rings and sprockets to more wear, biggest-biggest will also put a lot of strain on your rear derailleur pulley, and smallest-smallest will make the chain too slack. Just don't do it.
#15
Thrifty Bill
Join Date: Jan 2008
Location: Mountains of Western NC
Posts: 23,525
Bikes: 86 Katakura Silk, 87 Prologue X2, 88 Cimarron LE, 1975 Sekai 4000 Professional, 73 Paramount, plus more
Mentioned: 96 Post(s)
Tagged: 0 Thread(s)
Quoted: 1236 Post(s)
Liked 964 Times
in
628 Posts
+1 Don't cross chain, that's bad for any bike.
#16
Senior Member
Join Date: Apr 2009
Location: New Rochelle, NY
Posts: 38,712
Bikes: too many bikes from 1967 10s (5x2)Frejus to a Sumitomo Ti/Chorus aluminum 10s (10x2), plus one non-susp mtn bike I use as my commuter
Mentioned: 140 Post(s)
Tagged: 1 Thread(s)
Quoted: 5781 Post(s)
Liked 2,577 Times
in
1,428 Posts
The mechanic is giving it to you straight about a bit of runout being normal on cranks. These aren't made to aerospace tolerances so all have some degree of runout. Also flexing of the crank, spindle, and frame will cause the top of the chainring to move out a bit under heavy pedal pressure.
All that is factored into the width of the FD cage, so it should be possible to trim it for zero load in all normally used combinations, though you can expect some rubbing when crossed over to some degree, ie. the first on or two crossed over sprockets.
They could widen the cage to accommodate greater changes in chain angle, but that would worsen shift response so they focus on best overall performance based on the assumption that you wouldn't ride crossed over, except for very short intervals. Some systems have trimmable FDs, notably Campagnolo, that allow you to fine tune the FD position as you ride, but most indexable front systems don't.
As long as you get good, shift performance, and no rub in the commonly used gear combinations, your bike passes muster.
All that is factored into the width of the FD cage, so it should be possible to trim it for zero load in all normally used combinations, though you can expect some rubbing when crossed over to some degree, ie. the first on or two crossed over sprockets.
They could widen the cage to accommodate greater changes in chain angle, but that would worsen shift response so they focus on best overall performance based on the assumption that you wouldn't ride crossed over, except for very short intervals. Some systems have trimmable FDs, notably Campagnolo, that allow you to fine tune the FD position as you ride, but most indexable front systems don't.
As long as you get good, shift performance, and no rub in the commonly used gear combinations, your bike passes muster.
__________________
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
FB
Chain-L site
An ounce of diagnosis is worth a pound of cure.
Just because I'm tired of arguing, doesn't mean you're right.
“One accurate measurement is worth a thousand expert opinions” - Adm Grace Murray Hopper - USN
WARNING, I'm from New York. Thin skinned people should maintain safe distance.
#17
Senior Member
Join Date: Feb 2004
Location: St Peters, Missouri
Posts: 30,225
Bikes: Catrike 559 I own some others but they don't get ridden very much.
Mentioned: 16 Post(s)
Tagged: 0 Thread(s)
Quoted: 1572 Post(s)
Liked 643 Times
in
364 Posts
Brand new bike? Purchased from a bike shop? Don't be upset, just take it back to the shop.
You pay a hefty premium when you buy a new bike from a shop (versus a used one off C/L or whatever). Part of this premium is having someone to stand behind it. You paid for that service, I would use it.
Once you start tweaking on stuff, if you are unsure what you are doing, you could just make it harder for the bike shop to sort out.
You pay a hefty premium when you buy a new bike from a shop (versus a used one off C/L or whatever). Part of this premium is having someone to stand behind it. You paid for that service, I would use it.
Once you start tweaking on stuff, if you are unsure what you are doing, you could just make it harder for the bike shop to sort out.
There are several front derailleur adjustments. They have to be done in order because each one affects the subsequent adjustments. If you're not pretty sure of what you are doing - do your bike mechanic a favor and take it back to him before monkeying with it.
#19
Constant tinkerer
Glad to hear you got it fixed. As everyone has said, don't use the cross combinations! Bad for your chain, sprockets, derailers (if they rub). Bad for everything! Other than that enjoy your new bike.
Thread
Thread Starter
Forum
Replies
Last Post
homeriscool
Road Cycling
34
04-11-13 07:55 AM