Fat Tire & Clearance issue. Traffic, hills, and rambling questions

jolfstn

Member
Oct 30, 2011
112
1
18
Seattle, WA
This is my 2nd build, and I purchased this as the bike base:
FMGTalloy.JPG
This issue is the 3" wide tires, which I'm sure will go far as smoothing out the ride goes, however, the standard spoke mounted rag joint doesn't have the necessary clearance. I've tried turning the sprocket over so the teeth are pointed outward but still need more clearance. By eye, I also doubt that adding spacers to the spoke mount will provide the needed clearance. I was considering one of the hub sprocket drum brake assemblies I've seen for sale, as I removed the included coaster brake necessary to fit the sprocket so need brake options anyway, but would very much like to be certain the clearance will be present prior to purchase. This bike is a popular one, I've seen SBP Jack-shaft shift kit builds that were successful on this model, however, I purchased the single speed so a jack-shaft shift kit would not be practical, also I had one on my first build and wanted to avoid it this time. What is the best method for dealing with fat tires and no clearance with a standard left side drive chain? Those Sand Bikes with the 6" tires, I'm sure those are popular builds, how is it dealt with in that situation? I've kind of hit a wall, and like most of us I'm on a very limited budget. If possible and practical, I wish to keep the original tire but if necessary, if it's the most practical & least expensive option, I will consider simply putting a skinnier tire on my bike. this is back burner, I want to keep the fat tire if I possibly can. Perhaps one of you has built this very bike, or one like it with extra wide tires. How did you get around this problem? Thank you all for any input, I've been away for some time, having sold my last build and just recently getting around to this one. Please help! Keep in mind finances are limited but I would like the best option. This bike will be used to commute to work in a hilly urban environment, lots of traffic and stop lights. This leads to another question. One is stopped at the bottom of a hill, dead stop, say at a light or stop sign. It can be very difficult to build the necessary momentum going uphill to engage the motor fast enough especially contending with rush hour traffic. My previous method was to find an often less used out of the way route but was unavoidable at times to impede traffic which was uncomfortable for both me and those sharing the road. How do y'all deal with it? This is secondary, obviously, as it's not an issue until I get my machine running properly to begin with. Thanks for reading!:-||
 

scotto-

Custom 4-Stroke Bike Builder
Jun 3, 2010
6,508
11
38
Ridin' inSane Diego, CA.
You may have to spread the dropouts a bit and add spacers to the axle. This can also lead to another problem of proper chain alignment. You just might have to run narrower tires.

With a 2.3"-2.5" tire you shouldn't have much problem with tire and seat stay/ chain stay clearance and thems wide enough on the proper rim.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
16
0
memphis Tn
If you are on a budget, you can easily space the sprocket out more by using two or even three rubbers under the sprocket. I did this with a Jesse James chopper build to clear the 3'' tires with mixed results. I've also seen people make a hard plastic spacer drilled for the ragjoint. This seems a bit more secure to my thinking.
I used two rubbers but the chain still marks up the tire. Three rubbers or a plastic spacer would have been better.
I had no issues with it loosening or moving at all and I'm 250lb +.

However, a moped or HD hub wheel specially built for your needed clearance would be a much nicer fix.
 

2door

Moderator
Staff member
Sep 15, 2008
16,335
141
63
Littleton, Colorado
Although I've never had to do it, but a good bike wheel man can 'dish' the spokes which will move the rim off center. That might be an option to explore.

I have two bikes with 3" rear tires and don't have tire chain interference. One has a rag joint, the other a sprocket adapter. Both of these bikes however required the engine to be offset to the left for proper chain/sprocket alignment.

Have you actually mounted a sprocket and laid a straightedge against the sprocket to see where the chain will ride? Or are you just eyeballing it? You might have more clearance than it appears.

Tom
 

windtrader

New Member
Apr 14, 2014
2
0
1
ca
How does that bike ride with them fat tires? I've been looking at that same bike but can not decide how it will handle.

Does it soften the ride quite a bit while not reducing rolling resistance?

How much "sluggishness" is added due to the extra weight of the fat tire?

Will a machined sprocket adapter fit to go left side drive?
 

kevyleven007

Active Member
Sep 25, 2008
1,217
7
38
texas
I would think you would either have to go with smaller tires or offset the motor. You should have got the multi speed version. Those tires are great,,for an electric or multi speed shifter,, not so great for single speed gas. Good bike bad plan. Next time think it out a little better before hand. Lol. Actually its not that bad just offset the motor it shouldn't be too hard. After you fix the coaster brake back that is
 

Velodrome

Well-Known Member
May 27, 2011
2,387
216
63
Phoenix-ish
Although I've never had to do it, but a good bike wheel man can 'dish' the spokes which will move the rim off center. That might be an option to explore.

I have two bikes with 3" rear tires and don't have tire chain interference. One has a rag joint, the other a sprocket adapter. Both of these bikes however required the engine to be offset to the left for proper chain/sprocket alignment.

Have you actually mounted a sprocket and laid a straightedge against the sprocket to see where the chain will ride? Or are you just eyeballing it? You might have more clearance than it appears.

Tom
+1 on what Tom say. I built a Felt Chief with belt drive 3" Thick brick tires on 50mm felt rims. ( Whizzer schive ) which is a lot wider than chain drive and the only way it would work was to dish the wheel to the right and move the motor to the left. Worked really well.
 

maniac57

Old, Fat, and still faster than you
Oct 8, 2011
4,484
16
0
memphis Tn
I was able to mount the engine centered on the Jesse James, but just barely. Any larger tire would have required offset. The WCC's are 20'' rims. I have no experience with 3'' tires on bigger wheels.
 

The_Aleman

Active Member
Jul 31, 2008
2,655
3
38
el People's Republik de Kalifornistan
I would think you would either have to go with smaller tires or offset the motor. You should have got the multi speed version. Those tires are great,,for an electric or multi speed shifter,, not so great for single speed gas. Good bike bad plan. Next time think it out a little better before hand. Lol. Actually its not that bad just offset the motor it shouldn't be too hard. After you fix the coaster brake back that is
I agree with this guy. When mounting a chinagirl with a ragjoint, your cheapest solutions regarding wide tires are a narrower tire
or offset-mounting the engine.

Next up is is an alternative sprocket mount or what 2door said: re-dishing the wheel. You pay a price for those fat tires with stock mount!

My opinion: narrow (read 1.5-1.95) tires may not look as great, but you will get more speed out of em and the clearance to make it work
with least headache.
 

insomniacshotrods

New Member
Sep 26, 2008
78
1
0
I used a rear rim set up for a disk brake then got a sprocket to fit the rim and had no problem when using the thick brick 3 inch tire. Other 3 inchers would not clear the chain. Kept motor in stock location even.

 

windtrader

New Member
Apr 14, 2014
2
0
1
ca
Is that standard width on the rear? If that was wider than a larger tire would probably fit. Where did you get that sprocket? Looks quite nice.
 

insomniacshotrods

New Member
Sep 26, 2008
78
1
0
Yes it is a stock width 24 inch rim for a disc brake bike. Like I said the other 3 inch tire brands all hit the chain or the frame or both. Only the thick brick would work with out modding for clearance.
 

insomniacshotrods

New Member
Sep 26, 2008
78
1
0
This was how it looked when I built it 6 yrs and 700 miles ago. Still needed to tie the cables down in this pic. I put a speed carb on changed to a 40 tooth sprocket on, ported the intake/exhaust and cut the pipe inside the exhaust off even to get better flow. Got up to 43 mph according to mobile police radar station. I just built it to beat my buddies bike that had a 3spd and a nitrous kit. I was building a nitrous kitted bike with a 7sp in case this one didn't do it , but it did ha. I let my son ride it and he put it in a ditch bending both rims so I started on the fat tire project.

 

SuperSean310

New Member
Jan 24, 2015
11
0
0
OC California
Sorry to hijack your thread but I have the same bike Insomniac. How does it hold up? Check mine out! I run a 2.5 inch tire with no contact with the chain, Where did you find a 24 x 3 tire? That seems like it would be a good setup. Nice bike
 

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jhammondcpa

New Member
Apr 17, 2014
12
1
0
Maryland
Been there and done that with the same bike and tires. I added the 3 piece sprocket to get the chain out as far as I could at the rear and then I made special engine attachment pieces to shift the engine left in the frame by 1/2 inch. That made the 3" tires work, but barely. I ended up going with 2.3" tires which is what most full time builders use as a limit. I have attached a few images that help me explain. You can see my two finished bikes here: https://www.youtube.com/user/JimConHam/videos
 

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