What a glide actually carries
An empty dining chair puts about 9 kg on the floor through four feet. With a 78 kg guest seated the static load per glide is roughly 22 kg. The number that matters is not the static one: a guest who lowers into the seat rather than sitting down produces a peak near 1.8 times static, and a chair dragged sideways while occupied transfers most of its load onto two legs at an angle. Specify for 40 kg per glide and you have covered the ordinary restaurant case with margin.
Contact area is where the pressure is decided. A 25 mm disc has a footprint of about 490 mm2, so 40 kg sits at 0.8 MPa. A 12 mm nail-on glide has 113 mm2 under the same load and reaches 3.5 MPa. That figure is above the compressive strength of a soft luxury vinyl tile, which is typically rated to resist 0.10 mm of indentation under a 500 psi load, and four times above the point where an engineered timber wear layer takes a permanent dent. The difference between a 12 mm and a 25 mm glide is not cosmetic; it is the difference between a floor that recovers and a floor that does not.
Then there is travel. In a 200 cover room a chair is moved 60 to 120 metres a day: pulled out, pushed in, shifted for cleaning, moved for a party of nine. Call it 30,000 metres a year. That is the wear budget a glide has to survive, and it explains why a pad rated for 10 years of domestic use fails in 18 months in a restaurant.
Five pad materials, and the floor each one suits
Nylon, usually PA6 at 30 to 35 Shore D, is the default on metal frames. Its friction coefficient on dry porcelain is around 0.15, so the chair slides predictably, and it wears 0.08 to 0.12 mm per 10,000 metres on a hard floor. The failure mode is not wear, it is embedding: a 0.2 mm quartz grain pressed into the nylon at 0.8 MPa turns the pad into a cutting tool, and the first scratch appears on the floor before the pad looks worn at all.
Polypropylene is the cheaper option and the one that causes the most callbacks. At 20 to 25 Shore D it creeps under sustained load, and in a room held at 28 to 30 degrees it flattens by 0.3 to 0.6 mm within 12 months, so the chair starts rocking on three legs. If the quote is 0.04 dollars per glide rather than 0.09, it is usually this material.
Felt, a 5 mm wool and polyester blend, is the quiet choice and the right one for engineered timber, terrazzo and polished concrete. It drops the sound of a chair pull from the high sixties to the low fifties in decibels. Its weakness is that felt is a filter: it collects grit, holds it, and then abrades the floor with it. In a 200 cover room, felt glides on a hard floor need replacing every 6 to 14 months, and the check is visual, because a contaminated felt pad looks intact.
TPU at 85 Shore A is the grip option, used where chairs must not slide, on ramps or on a mezzanine with a slight fall. On vinyl it is the wrong choice: plasticiser migration from the pad marks the surface within 3 to 6 months in a warm room, and the mark does not clean off. Save TPU for carpet and for outdoor terraces.
Steel or brass feet with no pad belong on carpet only. On any hard floor they transmit every particle of grit straight through a contact patch of 50 mm2, and they are the single most common cause of the deep gouges we are asked to comment on. When a client sends a photograph of a scratched floor and a chair with bare metal feet, the conversation is short.
Floor by floor: what to fit and what to expect
Ceramic tile with 8 to 10 mm grout joints is the most forgiving hard floor and the one that punishes small glides most. A 25 mm disc bridges a 10 mm joint because the joint is under half the disc diameter; a 12 mm nail-on drops into it, chips the joint edge and, once the joint is open, lets water into the screed. On a tile floor with wide joints, specify 25 mm minimum and check that the joint width stays under 60 percent of the disc.
Rectified porcelain at 6 mm, with a Mohs hardness around 7, is harder than any polymer glide. The floor does not wear, the glide does, and it wears faster than the tables suggest because porcelain is also slightly abrasive. Expect nylon to need replacement every 18 to 24 months on porcelain in a busy room, and buy the glides as a consumable line item rather than discovering it at year two.
Luxury vinyl tile with a 0.55 mm wear layer is the floor most sensitive to point load and to chemistry. Keep the disc at 22 mm or more, avoid TPU and rubber entirely because of plasticiser migration, and specify a nylon that will not take a permanent set. A 0.8 MPa load on a 20 mm disc is inside the rating; the same load on a 14 mm disc is not, and the resulting dimples are visible under raking light from the moment the room opens.
Terrazzo and polished concrete are abrasive in a way that surprises buyers. The aggregate is silica at Mohs 7 and it acts like a grinding wheel on any polymer. Felt glides on terrazzo in a 250 cover room last 4 to 6 months before the pad is through to the fixing. Plan for quarterly replacement and buy 12 months of stock at handover.
Engineered oak with a 3 mm wear layer sits in the middle: felt is correct, nylon is acceptable if the disc is 22 mm or wider, and bare metal is never acceptable. The same glide question applies to restaurant chairs and stools, where a 25 mm disc on a 42 mm leg gives a stable footprint and a 16 mm disc on the same leg does not, regardless of how the chair is used.
The scratch is usually grit, already on the floor
When a client reports a scratched floor the instinct is to blame the glide, and the glide is usually innocent. Silica particles of 0.1 to 0.3 mm, tracked in from a car park or blown in from a street, sit between pad and floor. Under 22 kg per leg the contact pressure at the particle tip passes the yield point of any floor finish, and the chair then drags that particle 300 mm. A single grain does this once; a hundred grains do it every service.
That is why entrance matting, not glide specification, is the highest-return fix. Two mats of 900 by 1500 mm at each entrance, one coarse and one fine, remove 70 to 80 percent of tracked grit before it reaches the dining room. Add a 15 minute sweep of the dining floor between services, and the scratch rate on a vinyl floor drops by more than half in our own project records.
The second cause is cleaning chemistry. A floor stripped with a strong alkaline and left unsealed has a surface that grips rather than releases, and the chair then tears at it instead of sliding. If a floor suddenly starts to show scratches across the whole room rather than in the traffic lanes, look at what changed in the cleaning routine before replacing 200 glides.
The noise question, in decibels
Noise is measurable and it is worth measuring, because a 12 decibel difference is the difference between a room where guests lean in and one where they raise their voices. Pulling a chair one metre across a dry porcelain floor reads 66 to 68 dB with hard nylon, 60 to 62 dB with TPU, and 50 to 54 dB with 5 mm felt. Dropping a chair from 30 mm reads 74 dB with hard nylon and 61 dB with felt, and the drop is the sound guests actually notice, because it happens 40 times an hour at a full room.
Felt is not a universal answer. On a carpeted floor felt is pointless, and on a floor that is mopped nightly with a wet mop, felt stays damp and compresses to 2 mm within a season. On tile and porcelain in a wet-cleaned room, TPU or a soft nylon with a 1 mm elastomer insert gives most of the noise benefit with none of the moisture problem. That insert option adds about 0.12 dollars per glide and it is the one upgrade we recommend most often on acoustic grounds.
Five lines on the purchase order, and a replacement interval
Write the glide into the order as a specification, not as a factory default. Five lines are enough: pad material and hardness, disc diameter, fixing method, floor type it has to run on, and the replacement interval in months. A mill that cannot tell you the Shore hardness of its standard glide is fitting whatever was in the bin, which is common and is not necessarily wrong, but it is not something to discover after the floor is laid.
Fixing method matters more than buyers expect. A nail-on glide sits in a 3 mm hole in a timber leg and pulls out when the chair is dragged sideways, which is why so many wood chairs arrive at year two with two glides missing. A screw-in glide with a 10 mm thread, or an insert fitted at the factory with a 0.5 mm interference, survives the side load. On a metal frame, a push-in glide with a ribbed shank at 0.3 mm oversize is the reliable pattern; a plain shank falls out at the first drop.
Set the replacement interval from wear, not from failure. Measure the pad with a caliper at handover and again at 6 months. When the thickness has dropped by 0.5 mm, or the pad has taken a visible flat on one side, replace the set. That is the point at which the pad stops spreading load and starts concentrating it, and it is 6 to 12 months before the floor shows damage. Every one of the commercial dining chairs we ship is documented with the glide size fitted, so a replacement order two years later can be placed from the invoice rather than from a photograph.
Buy spares with the original order. Five percent of the chair count as loose glides costs a few dollars on a 150 chair project and it removes the six week wait that otherwise turns a 40 cent part into a scratched floor. Glides, feet and bumpers are the three consumables worth stocking, and they store in a shoebox.
Two builds, and the reasoning behind each
The JP-C018 metal dining chair leaves the workshop with a 25 mm nylon disc in a ribbed push-in shank, because the aluminium frame is light, the chair is usually specified for tile or porcelain, and the wider disc keeps the load at 0.9 MPa. On the same frame we fit a 22 mm TPU pad when the project is going onto a timber floor on a first floor above a tenanted space, where the acoustic requirement outranks the sliding feel.
The JP-C005 wood dining chair uses a 5 mm felt pad on a screw-in base, and that is a deliberate choice for rooms where the floor is engineered oak and the chair is expected to last 5 years. The screw fixing exists because timber legs and side drag are a poor combination for a nail. On a 120 chair order this adds 36 dollars in total and it is the cheapest insurance in the specification.
Metal frames are where glides fail fastest, and it is one of the reasons we keep a wear test in the restaurant furniture quality control routine: 20,000 cycles of a loaded chair pushed and pulled on a porcelain plate, then the pad is measured and photographed. A pad that loses more than 1 mm in that test does not go on a production chair. If you are comparing metal dining chairs for restaurants from more than one supplier, ask for that number, and treat a supplier who cannot produce it as a supplier who has never measured.
If the floor type is not yet decided, request a restaurant furniture quote with the floor specification and the cover count per day. The glide, the disc diameter and the replacement quantity come back together, which is the only way to buy the part before the floor is on site rather than after the first scratch appears.