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Tyre size


Karlos28

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Hi all,

 

Fairly new to all this trials stuff, and have a quick question..

 

I have picked up a few spare bits and bobs.. some.of which are wheels. I have an onza T-Bird, and I tried to fit a spare set of wheels that look a bit better (still Onza)... The rear rim is wider with a creepy crawler on, but it was too wide and caught the chain. So, as the onza sticky finger is a little worn, I put the creepy crawler on the original, narrower rim.. but it still caught the chain. They are both 19(20)x2.5 tyres.

 

Is there something I am missing or will I only be able to use sticky fingers on it?

 

TIA

Karl

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  • 2 weeks later...
On 8/4/2020 at 9:26 AM, Karlos28 said:

Apologies for the delay... Some not great photos of the onza tyre fitted, only about 5-7mm of clearance between tyre and chain. The creepy-crawlers are a tad wider so it catches....?

IMG_20200803_171847.jpg

1) What's the dish like pal? Excessively towards the drive side? It will be asymmetric, yes, but only a tad. It shouldn't look like a >9speed with the driveside spokes near vertical. The dead give away would be when you set the slaves up the arbitrary 1-2.5mm from the rim (with a straight and correctly set wheel) and the non drive side drive is pushed in with the driveside one having to be set pushed out off into the next postcode.

2) What length bottom bracket have you in there? From that angle I'd tek a stab that you need longer one or an offset one because you've changed the chainline measurement by adding the front free wheel set up from that donor bike (green 06 Tpro, right?). 

See Ref. https://www.sheldonbrown.com/chainline.html.

The rear chainline has been changed because the rear freewheel would have sat the chain more towards the hub's centreline, also.

3) When I had my one of those T-birds (bought new, factory spec, MY05/6 T-bird in silver, onza reggie wheel, creepy crawler, 24/18 gearing, KMC K710 Kool chain) the tyre was bloody close to the chain, close enough that I recall cutting across the school playing field trying to make curfew one time & enveloping the chain is boggy grot.

4) Do an idiot check. Start afresh, run through all all the stupid shit that should be "right" such as tweaked dropouts, bent wheel axle, wonky BB axle, wonky freewheel with four miles of runout, wheel moving in the dropout as you give it the bigun on the spanner etc. and everything else that gets f**ked on 2nd/3rd/14th hand bikes. You haven't a scooby what Cletus may have been in there before you on either bike/combination and now you are trying to modify and merge the two. Nothing is a given.

5) What locknuts are those? 3, 5 or 7mm? You're getting desperate by this point if you need to do this but if those are 5mm locknuts you can do some fudgeing swapping the NDS locknut for a 3mm and the DS for a 7mm, with or without the application of penny washer(s), longer BB and taking some dish out of the wheel.

I do/have done faaarrr too much f**kin around with dirty old bicycles of all shapes and sizes that have had at least two goes round the sun and often many a 'tard piloting and spannering them >-]

Keep updating.

Ciaran.

Edited by CC12345678910
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Haha awesome reply Ciaran! Some really good points there.

 

1)

I honestly haven't looked at the dish that much as I am awaiting some new 4 bolt mounts (the lower half of one side is a V brake mount... How does that happen!?) Will definitely check it out though, I know the front. Has a fair few mm of dish, which I found quite odd...

 

2)

Errr, that's a tough one, 135 rings a bell? Being totally honest this was a bit of a guess as the original frame I got (long story) had no BB so took an educated guess...

 

I do have another square taper onza BB and cranks that had the original front freewheel (it actually has a double freewheel set up, quite impressively pointless!) From the T-Pro that I may try fitting, to see how it looks/rule out the BB length. They are 165cranks though... Not sure if that's good/bad/better/worse than the 175 tensiles I have now..

It wouldn't work with the rear chainring set up I originally had either, same BB... So you might be into something there...

The chain line looks really good though, not sure moving it outboard much would be a good idea... I guess that's why I never suspected BB length.

I have started a fresh a few times now as I have moved it through a couple of different set ups.. this is why I wondered if it's normal.. if you have had one on there, it must be something I am doing!

Wheel axle lock nuts? Not sure.. axle is only 10mm. I'd rather use this wider hog wheel, as it used Allen bolts to secure the wheel, I have ordered a couple.of chain tugs too so that I can make sure the axle is square.

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5ce2ba3d6cdd4b38406e8b9d

The original setup for the silver t-bird's looked like this. The black anodised framed ones ^ were the year after (2007) with the front disc brake but rear V brake (no 4 bolt mounts, no HS33's, no creepy crawler tyres, economic decisions appear to have been made). 

My recollection and educated guess would be that OEM set up used a crank with a higher (larger number/value, further away from the centreline of the bike), in order to use readily available and therefore cheaper per unit components such as a more standard 113mm or 118mm length BB axle and still make a respectable chainline in combination with the rear freewheel, but most importantly clear the what in other disciplines would be considered a daft wide rear tyre.

Now might time to say that if you are expecting arrow straight chainline like you would expect to achieve on other types of bike you are on a hiding to nothing. Short chainstay, big tyre, narrow overlocknut distance, mod chainline will always be shi*e to a certain degree. Think fat bikes - clearance for daft 5" tyre = 83 to 100mm BB shell and big chainline value. But Mods don't have 148mm+ frame spacing/OLN distance to aid chainline.

What you've done with the front freewheel set up is lowered the chainline value (the chain has gone toward the centreline of the bike), so my thoughts are that you now need to compensate with BB axle length. In this respect the idea that you have a 135mm ISIS or Square taper BB in there now is highly suspect (never heard of one). The increase of chainline value in the rear sprocket will be a good thing though unless the chain takes a snack full of seatstay/dropout. The frame was made around 24/18 ratio and you've 18/12 so real estate should be ample. 

127, 127.5, 128mm BB's are the trials standard in front freewheel (FFW) applications, 122.5mm can also be used, but any narrower and you will likely run in to clearance issues between the freewheel and BB cup or BB shell. If you have anything less that a 122.5mm bb in there at there at the mo I'm amazed you aren't taking lumps out of the BB or frame (or have you not cinched the cranks down fully yet?)

What is the complication with the two cranks, why can you not put the tensiles on the taper BB? or are the tensiles ISIS?

The mention of the axle locknuts was a desperation time ploy that I have used before as you would move the hub therefore entire wheel and ultimately the tyre laterally 2mm toward the non drive side then though a combination of fiddlef**king around with dish, BB length, higher chainline value and, in last resort shit or bust thought process, adding drive side penny washers and ramming the wheel in, splaying the frame and spacing the driveside V-brake arm out so I can add stupid dish (Do not ever do this :giggle:, least not to something that isn't a gas pipe like steel frame) Yeah yeah I'm a dodgy pr**k I know, needs must...

Edited by CC12345678910
Typos, Freudian slips
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I had exactly the same issue when I had the freewheel on the rear hub... With the tensile cranks.

Correct the tensiles are ISIS, onza square taper. The cranks are tightened down fully, the freewheel is very close to the frame/BB shell, but it's not contacting. I will take the BB out and confirm the actual size.

Damnit! I have just sold a set of those exact cranks! Looking at them, they don't look much different from the tensiles with the chainring set up fitted like I used to have it, if anything I'd say the freewheel moves the chain line outboard, as there is no bash taking up space..

 

It's very odd, I think I'd put my money on the BB length as that was a bit of a guess/use what was in stock. I do have another square taper BB (also onza) kicking about actually... Might measure that up too.

 

Worst case, I will just run sticky fingers!

Edited by Karlos28
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On 8/6/2020 at 7:50 AM, Karlos28 said:

I had exactly the same issue when I had the freewheel on the rear hub... With the tensile cranks.

Sorry, I missed the bit about it not working with RFW in the other post.

Correct the tensiles are ISIS, onza square taper. The cranks are tightened down fully, the freewheel is very close to the frame/BB shell, but it's not contacting. I will take the BB out and confirm the actual size.

Damnit! I have just sold a set of those exact cranks! Looking at them, they don't look much different from the tensiles with the chainring set up fitted like I used to have it, if anything I'd say the freewheel moves the chain line outboard, as there is no bash taking up space..

Okay... Well, that's not what I pictured in my mind, but you have the stuff all there in front of you and I'm doing it from fading memory.

It's very odd, I think I'd put my money on the BB length as that was a bit of a guess/use what was in stock. I do have another square taper BB (also onza) kicking about actually... Might measure that up too.

https://www.ebay.co.uk/itm/Tensile-Sealed-Bearing-Isis-B-B-NEW-68-or-73mm-Shell-127mm-Axle-Length-Value/353124681587?hash=item5237df0773:g:dFUAAOxygj5ShPa8 

I've bought these from the boys in Nottingham for years, they're no worse than anything else, weight aside, and when you bend em or a bearing shatters (internal BB life) you just chuck another in there like a cassette. After 2 or 3 go cactus I just make the next one up out of the leftovers and go again. 

Worst case, I will just run sticky fingers!

Yeah... They're pretty crap but better that and be riding about than owning some yard art. The creepy should fit though - my t-bird one came with one on it from the showroom. The only other variable I can think of is that mine had a 43mm Reggie rim in the back, if your rim is wider then the tyre could "grow", as in pump up large and take away sidewall to chain/chainstay clearance. Likewise a 38mm rim could pinch the tyre and that has scope to make the side nobbles catch. All v. unlikely, but plausible non the less. 

 

Edited by CC12345678910
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Again cheers for the reply fella!

 

Well.... I did as you said, back to basics... Stripped it down, checked it all out (forgot to look at BB size!).. all fine, put it back together with the onza hog (wider) rear wheel + creepy crawler this time.. worked absolutely fine. Chain line is good, tyre is central and clear.... However the rim is too wide for the hs33 to work!! So, chucked the creepy crawler on the other rear wheel, all works like a dream!?

 

God only knows that I was doing wrong..... I tried it several times, on the two rims! 

 

Thanks again for the tips and advice!!

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On 8/4/2020 at 10:45 PM, CC12345678910 said:

1) What's the dish like pal? Excessively towards the drive side? It will be asymmetric, yes, but only a tad. It shouldn't look like a >9speed with the driveside spokes near vertical. The dead give away would be when you set the slaves up the arbitrary 1-2.5mm from the rim (with a straight and correctly set wheel) and the non drive side drive is pushed in with the driveside one having to be set pushed out off into the next postcode.

2) What length bottom bracket have you in there? From that angle I'd tek a stab that you need longer one or an offset one because you've changed the chainline measurement by adding the front free wheel set up from that donor bike (green 06 Tpro, right?). 

See Ref. https://www.sheldonbrown.com/chainline.html.

The rear chainline has been changed because the rear freewheel would have sat the chain more towards the hub's centreline, also.

3) When I had my one of those T-birds (bought new, factory spec, MY05/6 T-bird in silver, onza reggie wheel, creepy crawler, 24/18 gearing, KMC K710 Kool chain) the tyre was bloody close to the chain, close enough that I recall cutting across the school playing field trying to make curfew one time & enveloping the chain is boggy grot.

4) Do an idiot check. Start afresh, run through all all the stupid shit that should be "right" such tweaked dropouts, bent wheel axle, wonky BB axle, wonky freewheel with four miles of runout, wheel moving in the dropout as you give it the bigun Tutuapp on the spanner etc. and everything else that gets f**ked on 2nd/3rd/14th hand bikes. You haven't a scooby what Cletus may have been in there before you on either bike/combination and now you are trying to modify and merge the two. Nothing is a given.

5) What locknuts are those? 3, 5 or 7mm? You're getting desperate by this point if you need to do this but if those are 5mm locknuts you can do some fudgeing swapping the NDS locknut for a 3mm and the DS for a 7mm, with or without the application of penny washer(s), longer BB and taking some dish out of the wheel.

I do/have done faaarrr too much f**kin around with dirty old bicycles of all shapes and sizes that have had at least two goes round the sun and often many a 'tard piloting and spannering them >-]

Keep updating.

Ciaran.

Nice guide, it helped me too. Thanks

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