There is a category of cycling question that almost nothing online answers properly. Not because the answer is secret, but because the answer is specific to your bike - and a product page, a forum thread from 2019, or a generic buying guide can't be specific to your bike.
We've had an assistant running on the site for a while now, and we've named it TBA Guide. It's free, needs no sign-up, and sits on every page. But this article isn't really about the tool. It's about the questions themselves, because most of them have good answers that hardly anyone writes down.
"What thru-axle do I need?" is the worst one
Ask the internet what thru-axle fits a 12x142 rear hub and you'll be told 142mm. That is the wrong number to order on, and it's wrong in a way that costs you money.
12x142 tells you two things: the axle is 12mm in diameter, and your hub is 142mm wide. It does not tell you the full length of the axle, which varies because dropout thickness differs between frames. One frame we list specifies rear thru-axle X12 / 142mm / full length 160mm. Another 12x142 frame will want something else.
Thread pitch varies too - M12 x 1.5 on some frames, other pitches elsewhere. Order an axle with the wrong pitch and it will bind in the dropout. Force it and you damage frame threads, which on carbon is an expensive afternoon.
So to buy a replacement axle you need three things: 12mm diameter, 142mm hub spacing, and your frame's thread pitch and full axle length. The first two are on every listing. The last two are on almost none, which is exactly why this goes wrong. We wrote it up properly in our thru-axle and quick release reference.
"What frame size am I?" - where the honest answer is a range
Ask most sites and you'll get a single number from a generic chart. Ask about 5'9" with a 32" inseam and the real answer is that it depends on the brand and on how you want to ride.
Across the size guides we hold: Felt road bikes put a 54 at 5'8"–5'10" with a 30.7"–32.3" inseam. Colnago lands around a 485 for 5'9" with an 81–83cm inseam. Kona road and gravel generally sits at 54–56cm in that range.
So the safest starting point is 54cm - with 56cm worth considering if you prefer a relaxed position, and 54cm the better bet if you want something aggressive. Three brands, three ways of describing the same rider. That's why a single number from a generic chart is usually not enough, and why our frame sizing reference lists the brand charts individually rather than averaging them.
Compatibility questions, where the answer is genuinely binary
Will a Shimano 105 R7000 cassette work with an Ultegra freehub? Yes, the R7000 is an 11-speed road cassette, and Shimano's road hubs use the HG road freehub, which takes it. That's a real answer, and it's the kind of thing that takes twenty minutes of forum-reading to establish otherwise. More of these in our freehub and cassette reference.
Can you fit 32mm tyres on a Basso Venta? On the Venta R models we carry, the stated clearance is up to 35mm, so 32mm sits inside the limit - with the caveat that measured tyre width varies a little with rim width and tyre model, so "stated clearance" and "what your specific tyre measures" aren't quite the same thing.
Helmet sizing is similar. At a 57cm head, Giro's Adult Super Fit medium covers 55–59cm, and their Adult Universal covers 54–61cm, so either works depending on how the specific model is sized. Which is more useful than "medium probably." Browse helmets if you want to check a specific model.
The answers we're most pleased with are the ones that say no
Ask whether Northwave shoes run small and TBA Guide will tell you it can't confirm that from our size guide. It won't invent a view. What it gives you instead is the actual chart - EU 43 is 27.8cm foot length, UK 9.5, US Men's 10.5 - and the more useful advice, which is to measure your foot in centimetres rather than trusting your usual shoe size. Foot length is the number that matters; shoe size is a proxy that varies by brand. Our cycling shoes all list their charts.
Ask for a brand we don't stock and it says so plainly. Ask for Rapha and you'll be told we don't carry it, followed by what we do have in that space - Santini, Assos, Monton - rather than a deflection. Ask whether a specific bike is available and if it isn't, it'll tell you that too, and offer the nearest thing we can actually sell you.
An assistant that only ever says yes isn't much use when you're spending money.
Where it knows things a generic tool wouldn't
Ask how to protect your drivetrain through monsoon and the answer isn't "wash your bike." It's that rain itself isn't the main problem - the damage comes from lube washing off and road grit taking its place, and that combination wears chains, cassettes and chainrings far faster than water alone. So: wet lube rather than dry through the season, wipe and re-lube after every wet ride, degrease weekly, check chain wear every two to three weeks.
Ask about fuelling a 100km ride in Indian heat and you get numbers: a gel every 35–40 minutes, salt capsules every 60–90 minutes, 750ml to a litre of fluid per hour alternating plain water and electrolyte, 500–700ml of electrolyte drink about an hour before the start, and start fuelling within the first 45 minutes rather than waiting until you feel hungry.
Neither of those came from a product feed. They came from our monsoon maintenance guide and our race-day nutrition guide, written by people who ride here - the nutrition one by Gokul Krishna, an ABCC-certified coach. TBA Guide reads what we publish, which means every guide we write makes it better at answering this kind of thing.
When it can't help
Sometimes it won't have the answer. When that happens it takes your details and the question and emails it to us, and someone replies. It doesn't guess, and it isn't a substitute for talking to a mechanic about your specific bike - for anything structural, or anything where getting it wrong is expensive, come to the workshop in Kondapur or message us.
It's the icon in the corner of every page. Ask it something awkward.
FAQ
What is TBA Guide?
An AI assistant on thebikeaffair.com that answers questions about products, sizing, compatibility and riding. It draws on our full catalogue and on the guides we publish. It's free and needs no sign-up.
Does it cost anything or need an account?
No to both. It's on every page of the site and you can use it without signing in.
What thru-axle length do I need for a 12x142 rear hub?
12x142 gives you the axle diameter (12mm) and hub spacing (142mm), but not the full axle length, which depends on your frame's dropout thickness. Thread pitch varies too. To order a replacement you need all three: diameter, hub spacing, and your frame's thread pitch and full axle length.
What frame size do I need at 5'9" with a 32" inseam?
54cm is the safest starting point for a road bike. 56cm may suit if you prefer a relaxed position; 54cm is better for an aggressive one. It varies by brand - Felt sizes a 54 for 5'8"–5'10", Colnago is around a 485 at that height, Kona generally 54–56cm.
Can it tell me if something is in stock?
Yes. Ask about a specific product and it will tell you whether it's currently available, and suggest a close alternative if it isn't.
What happens if it doesn't know the answer?
It collects your details and the question and emails them to us, and a person follows up. It won't guess.
Can it help with an existing order?
Yes. Ask about your order and it'll take your order number and email address so we can check the status.
Does it replace talking to a mechanic?
No. It's good at sizing, compatibility and narrowing down options. For anything structural, anything specific to the condition of your bike, or anything where a mistake is expensive, come to the workshop or message us directly.
