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Width of a 27 1-1/4 inch tyre

by j_vora
Mon, Nov 23, 2020 23:57
5

Hello : 

Would anyone know the width in mm of a 27 1-1/4 inch tyre ?

Is it 1.25 inches equivalent in mm ( ie 31.75mm ) - Or some other number ?

I am trying to “compare” the ride quality of a bike I used to ride eons ago on similar road conditions that I will once again ride on with a contemporary bicycle that I will purchase shortly. 

I do understand this is not an equal comparison for the different frame materials ( perhaps even tyre technology etc. ), but as I mainly have the previous experience to work with I am trying to arrive at some “base-line” in terms of ride-quality I can expect based on tyre width.

This is important as I have narrowed down my choice to 2 frames - One that can accommodate 28C & the other to 32C & hope to “match” the earlier ride experience.

I also appreciate that this is just one variable among a few others that will be considered as I make the final decision on the optimal bicycle to purchase. 

Hope some of you have an answer to my above question. 

Thanks in advance. 

Jai

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5 comments

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HoarseMann | 3 years ago
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Well I popped out to the garage and grabbed the calipers - an old 27-1-1/4 came up at 29.5mm and some newer Conti GP4000 28C's came up at 30mm.

I would say though, that the old bike is more comfortable than the new one - even with the 28C's run down at 50-60psi. But obv. a lot slower!

Like you say, there are more factors than just tyre size - chromed steel rims vs alloy. Steel fork with a huge trail and loads of flex. Then there's just the sheer weight of the old bike - that seems to deaden road buzz.

I'd go with the frame that can take 32C's, then you've got the flexibility to up a tyre size or fit guards. I've had 32C G-One's on the newer bike and they're probably closer to the ride quality of the old bike.

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wycombewheeler | 3 years ago
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in the absense of other deciding factors a frame that can accomodate a 32mm tyre, will accomodate a 28mm tyres and mudguards. So that would be my choice.

Also yes, I would expect the 32mm tyre to be very close to the 1 1/4" tyre from the past. However not all 28mm tyres will give the same ride quality, there will be variations in materials for improved weight, or grip, or durability, and these factors will also have a bearing on ride feel.

Agree with the comment on tyre pressure, as tyre width goes up, pressure comes down. 

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OnYerBike | 3 years ago
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Remember that you can always run 28mm tyres on the frame that can accommodate 32mm tyres, but not the other way around. So based purely on the limited information you have provided so far, I would lean in that direction.

That said, I agree that there are so many variables (not to mention the effect of the passage of time on your memories!) that I don't think your test will be very useful.

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Tom_77 | 3 years ago
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A 1-1/4 inch tyre would almost certainly be marked as 32C. If you were to measure the actual width that would vary depending on the width of the rim, tyre pressure, etc, and would probably be somewhere between 30 - 32mm.

I'm not sure how useful your baseline is. I have 28C tyres, if I pump them all the way up to the limit on the sidewall it's a pretty harsh ride, but if I let a bit of pressure out they're fine on most roads.

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j_vora replied to Tom_77 | 3 years ago
1 like

Thank you HoarseMann, wycombewheeler, OnYerBike & Tom_77  for taking the time to reply - You all have helped me and we all seem to be in agreement - Frame with can accomodate 32C is the way to go - Thats how it will be.

WIth appreciation,

Jai

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